The Cooper’s Hawk in Toronto 2020

COHA (m) in Humber Valley, Apr 18th at 11:20am, attending female near Nest #9.

A Chronicle of Courtship and Nesting:

My Interest in the Cooper’s Hawk

In Toronto’s Mimico Creek Ravine, from Dec 6th-Jan 10th, 2020, I had repeated low flight sightings of a Harlan’s Dark-morph juvenile (confirmed as a Harlan’s during the 2019 CBC). By January 13th, the Dark-morph had moved off but a Cooper’s Hawk (COHA) flew over my Mimico position then landed at a hunting perch high above a feeder. This classic COHA hunting strategy was also evident at my own home feeder and two other feeders in my area. Days later from the same Mimico position, still no Dark-morph but there was a second COHA fly over. I live in the neighbourhood where the uncommon Cooper’s Hawk can now be seen year round as its winter range extends northward. While I continued my local Dark-morph winter outings, the idea grew to focus on the COHA species as per its natural history and look for new breeding sites outside known COHA nests. It would be a good challenge to turn my sporadic local COHA sightings into regular observations on this agile woodland Accipiter. Plus while taking on this new COHA mission, I could still keep an eye out for the Harlan’s Dark-morph.

Scouting for Old Nest Sites of the COHA

Come February, I had started from scratch scouting for last season’s COHA nest sites as probable areas for 2020 activity. The scouting started in the heavily wooded Mimico Creek Ravine and Humber Valley. Winter scouting was good with water/land solidly frozen and bare deciduous trees for open views. Despite having to examine several dozen of the larger squirrel nests and a few sleeping racoons, I soon located potential COHA Nests #1 and #2 though these later fail to show any COHA spring activity. Followed next by Nest #3 (aka N#3), which had the most convincing structure and location. N#3 became a prime target for the upcoming COHA courtship. Meanwhile, I continued mid-day sweeps for old nests.

Potential COHA Nest #3, Humber Valley, Feb 16th. This rectangular shaped nest is 12m above the ground. Scale: main trunk diameter is 20cm.

Cannibalizing Old Nest Material

Nest #3, Humber Valley, May 15th, with 5% of nest material left. It was 100% complete on Apr 7th (as per the Feb 16th image).

During my winter COHA nesting, I located inactive Nests #1, 2&3. During the early breeding season Nest #3 have significant nearby calls and sightings while N#1&2 were inactive, period. As a casual followup on May 4th, I went to Nest #2 just to check it. While the tree was straight forward to find, the trunk crotch was 100% empty. Even the ground around the trunk was lacking any debris. This drove me to soon check N#3 and later N#1, which both had a fraction of their materials left with again, no debris around the trunks. If these three old nests were cannibalized for current nest building, potential local suspects could be the Cooper’s Hawk, Red-tailed Hawk, Great-horned Owl and Double-crested Cormorants:

  1. I have watched two pairs of COHA nest building (N#6&9) where they source only fresh twigs from local trees while ignoring nearby older nests, nor arriving from a distance with a large twig, etc.
  2. I have recently found (my second) active RTHA nest (N#14) which is 250m from last year’s RTHA nest (N#13) and also 350m from an inactive COHA nest (N#12). Both N#12 & 13 were intact.
  3. GHOW breed mid-winter and don’t seem the fit the timeline of this nest cannibalization except for maybe N#1.
  4. DCCO is a possibility given they are colonizing the Humber Marsh (approximately 1-2 km away from the 3 old nests). This DCCO nesting area from my observation has noticeably grown in size from 2018 to 2019. Using an Feb 19th, 2020 image from my winter scouting, there were at least 37 nest before the 2020 breeding season started. Finally, DCCO regularly fly over these well exposed N#1, 2&3 sites. To actually confirm what is going on, one could watch for real evidence next spring.

Urban COHA Courtship and Nesting

Hearing and/or finding, COHA in courtship activity was a key focus for reducing the legwork of locating this season’s nests. Once active nests were confirmed, they could be readily monitored through the nesting phase.

  1. Starting in late-February, COHA will call for mates and try to establish a nesting territory. They can be patterned. The thirty minutes before, until thirty minutes after dawn, is the preferred COHA breeding activity/calling time. Listen for “kik” & “cak-series” calls.
  2. A heavy overnight rain ending later in the morning, can also be very productive. I plan to arrive as the rain is just letting up. At this point, you will be mostly alone as many bird species become active with maybe 60 minutes before pedestrian traffic returns.
  3. If you have a COHA hotspot, finish dinner early, dress warmly and go for the 2-hours before the sunset until twilight. I have witnessed missing mates, a juvenile intruder, a hungry female try to catch a Mallard, always something.
  4. Walk slowly towards any distant call or low-overflight. Check horizontal branches of larger trees. Frequent stops, can be very productive.
  5. If a Turkey Vulture flies low over your target area, fully watch its passage. COHA will aggressively pursue this bird if it is near their nest.
  6. With my first-visual of a COHA, I pause-in-place to take everything in. There could easily be a second bird in play. Is there a pattern to the bird behaviour?
  7. I generally avoid putting excess pressure on birds, but have learned that COHA are very tolerant of human presence (at least in urban areas). However, there are limits.
  8. I prefer not to attract pedestrian commotion to my COHA hotspots. If an active nest has foot traffic nearby, I am discrete and avoid prolong stays or a string of daily visits.
  9. If a COHA hotspot suddenly goes dead for several days, I will then probe the wider area for the same birds (observing Nest #3 eventually led to COHA Nest #9, 250m away).
  10. To increase your COHA sightings, I keep field notes and avoid looking down to watch the LBJ’s.

Nest #4 in the Humber River Valley

On Feb 26th, I finally finished the mid-day nesting sweep of the Mimico Creek Ravine and Humber Valley. So on Feb 29th, I walked a significant length of Mimico starting at 6:30am but after an hour, still no calls. On Mar 2nd, At dawn, I was in the Humber Valley near Nest #3 and heard my first cak-series call ever!  Over the next four weeks, I never witnessed a COHA land on Nest #3. However, with each visit to the area I had multiple COHA calls, sightings and photos. Resent migration arrivals were probably also adding to the resident COHA population.

As a side note on the Nest #4 area, on Mar 4th I was listening for COHA calls when the dawn’s light caught a perching RTHA Dark-morph (resulting pictures have not been confirmed as a Harlan’s). For full Dark-morph details and three sets of pictures, see post at:

Two km further up the Humber Valley from N#3, a new COHA hotspot also produced results. When I entered a wooded area late in the morning on Mar 10th, heavy overnight rain was just ending. I approached a calling COHA (J#1). The cak-series calls had also attracted a high-flying COHA (J#2) that turned hard and dove in just missing the Juvenile #1. After a pause to perch for cak-series calls, an extended chase erupted with repeated loops and fast pursuit through the timber. Juvenile #1 always came back to hold its original perch. While this Flying Circus occurred around me, off at a distance, there was also a third COHA giving kik calls. It was quite a first-time event!

COHA (J#1), Humber Valley, Mar 10th at 11:28am. This agitated bird had just chased off COHA (J#2) and the two birds were actually staring at each other from 50m apart. Leads to my Mar 16th discovery of nearby Nest #4.
High-flying challenger COHA (J#2), Humber Valley, Mar 10th at 11:48am. This was the larger bird but also the apparent loser to the smaller Juvenile #1. Neither bird seem to care about my presence. Later, Juvenile #2 did flapped sideways to the next tree, when the established path took me 4m directly below its perch.

On Mar 10th, I had stood on a main path and despite the heavy COHA activity, I was unable to spot the nest in the dense canopy.  I returned to this area on Mar 16th and was determined to locate and photo the probable nest. With a change in tactic, I approach just after dawn from the opposite side of the target site, starting well back in the congested forest, I eventually picked up multiple COHA calls which drew me towards the exact same Mar 10th location. This tactic of taking a new direction-in, provided a view of nest activity and the image below:

Nest #4, Humber Valley, Mar 16th at 8:48am. A better view of a concealed nest, 15m above ground. Followed COHA calls in from deep cover, spotted COHA wing movement in hidden N#4.

On Mar 24th, I was in the Humber River Valley at Nest #4 before dawn. In the final approach along the main path, there was lots of activity and calls overhead. I saw a COHA adult close to a larger juvenile. Both were just below N#4. Standing in one spot just off the path, I had 30 minutes of action before before multiple talking pedestrians seemed to cool things down. Unfortunately after this date, N#4 activity abruptly stopped. I continued to monitor and fully probe the area but nothing except, within 5 minutes, two distant COHA flybys above private property at say 100-150m away. A lesson in how fast a hotspot can change.

COHA (J), Humber Valley, Mar 24th at dawn, just below Nest #4. Juvenile attend by a smaller adult, numerous “kik” calls from both birds. The adult kept changing perches around the juvenile and with difficulty, briefly landed on N#4 three times.

Hotspots that Suddenly Go Cold

On Mar 25-26th, the hotspot areas around Nests #3 & #4 both abruptly went inactive with no more COHA calls or nest activity going forward. It is understood that breeding COHA pairs may build more than one nest before settling on the location. But, could suddenly going inactive also be cause by a dominant COHA pair settling nearby and to establish their nest territory, would the dominant pair drive off any other COHA being observed at a hotspot?

Nest #6 in the Etobicoke Creek Ravine

I continued to probe the recently inactive areas around Nests #3 & #4 but on Apr 4th, put the new target of Etobicoke Creek Ravine into my COHA scouting rotation. This ravine was a short drive away and from my casual 2019 birding, it had similar elements to the Mimico Ravine & Humber Valley.

Potential COHA Nest #5, Etobicoke Creek Ravine, Apr 4 at 2:34pm. Inactive with loose litter on top, but a COHA was perched nearby.
COHA near Nest #5, Etobicoke Creek Ravine, Apr 5th at 10am. After 15 minutes, I choose to move-off given an abundance of foot traffic and off-leash dogs. Scouted in a 100m radius to N#5.
COHA Nest #6, Etobicoke Creek Ravine, Apr 5th at 12:00pm. N#6 was 17m up and 125m south of Nest #5. Finish scouting loop and depart the now very busy parkland.
COHA (f) near Nest #6, Etobicoke Creek Ravine, Apr 12th at 9:30-10:30am. Earlier had enter the wooded area with several loose barking dogs together with owners yelling at them to be quiet?!? Sat low on a log near N#5, at a distance spotted above COHA (f) in N#6, leaves nest twice for larger twigs, keeps within eyesight of N#6. Female frequently calls as a male appears and occasionally calls back. Male snaps smaller 5-10cm twigs, adds them individually to the nest when vacant.
COHA (m) near Nest #6, Etobicoke Creek Ravine, Apr 12th at 10:22am. Male attending female and gathering small twigs. As possible close-in behaviour, male not afraid to perch overhead and near my seated location. Still in my proximity, male goes out on thin branches and snaps the ends off. However, three times the male gets agitated with cak-series calls, heads east with more distant cak-series calls, then soon returns. Later while exiting 500m north, a pair of COHA (m) flew over in a tight pursuit. From the probable origin of the chase trajectory, this could have been the N#6 male and an intruder.

Nest #6, Etobicoke Creek Ravine, Apr 28th at 10:30am-12:09pm. COHA (f) in a very stationary extended sitting, low on N#6. It would appear that incubation has started. The male also stays in the area occasionally changing high perches. When just above the canopy, a soaring Turkey Vulture on an erratic fly gets within 50m of N#6, the COHA (m) launches and drives off the potential threat. Later, a steady RTHA passes 70m away and 20m above the canopy, the COHA (m) does not react. Finally on my wide scout around N#6, spotted an inactive potential Nest #10, 20m up and 60m east of N#6.

Followup observation trip to Nest #6, Etobicoke Creek Ravine, May 5th at 11:40-2:18pm. Neither bird seemed anxious or hungry. Initially the female is sitting in N#6. Male lands on the nest at 11:53am with the female getting up from her sitting. Female departs N#6 at 12:30pm while the male takes over sitting. Female tours & perches the local area out to 100m. After one low cak-series call, the female briefly returns/departs then eventually returns as per the “chip” image below. The sitting male (12:30-12:49pm) then finally departs. After some alterations, the female settles in and stays past my departure.

COHA (f) on Nest #6, Etobicoke Creek Ravine, May 5th at 12:46pm. Female with dark bark chip in beak, male sitting in the nest below the image sightline, soon departs.
COHA (m) below Nest #6, Etobicoke Creek Ravine, May 5th at 1:04pm. Close-in behaviour of male on third perch. Earlier on my approached, I locate N#6 at 11:40am and prepare my sit 40m out. As a surprise, also spot a settled male already perched 20m away & 20m up. Undisturbed by my arrival and setup, the male eventually departs at 11:50am to briefly join female at N#6. From 12:00-12:30pm, male returns to a second perch now 15m away & 15m up from my position. With the male’s third perch at 12:49-1:22pm, he lands on a ground log and is less than 10m away! This male is obviously aware of me but keeps very busy preening and rarely seeks a direct look. [Other close-in behaviours: Nest #6, Etobicoke Creek Ravine, Apr 12th at 10:22am and Nest #9, Humber Valley, May 8th at 1:20pm.]

Nest #8 in the Etobicoke Creek Ravine

Larger of two COHA, Etobicoke Creek Ravine, Apr 6th at 11:55am. 2km from N#5, initially had chased off a Turkey Vulture and immediately perches with calls. Meanwhile in this immediate vicinity, a smaller COHA (m), power-glides down to attack something 60m across the creek and flies out of sight. The larger COHA (f) next moves 50m to where I got this image of it staring at the N#7 below.
Potential Nest #7, Etobicoke Creek Ravine, Apr 6th at 12:01pm. N#7 was 12m up, a bit congested with branches and nest is ragged on top. This nest is located 30m from the larger female COHA’s second perch. Note the similarities of N#1, #3 & #7: rectangular shape with 20-40cm parallel stiff twigs (butts 0.5-0.9cm), 12m up, plus all three are inactive. COHA may not have made these large structures.
Nest #8, Etobicoke Creek Ravine, Apr 12th at 11:37. N#8 is 18m up but atop paved path! This site is 50m from N#7 and 2km from the N#5. Nest building COHA (f) departs for the next twig.
Nest #8, Etobicoke Creek Ravine, Apr 12th at 11:40am. COHA (f) doing mid-day building, lands with 20-30cm twig, after after 5 minutes of fitting, departs nest again. This overcast image could have been crisper if I used a tripod but that would draw significant pedestrian attention.

Nest #9 in the Humber Valley

Before the Nest #3 area went totally inactive, there was an initial 4-weeks of steady COHA calls with sightings of both adults and juveniles. However, there was no specific pairing or nest building activity. This was impetus to check the broader area. After 2-weeks of nothing, on Apr 7th, I was bisecting the area when I had a COHA fly through the tall mast of mature trees. I carefully stalked the trajectory, then heard distant calls. The new target was located 250m from N#3. As I stalked much closer to the kik and cak-series calls, I chose to sit on a log and use my Binos. I was soon drawn to the tallest tree in the area and yes, two adult COHA (m/f). This new hotspot, led me on Apr 13th to spot the COHA (m/f) feeding on an active Plucking Post. As a bonus, the COHA (m) showed me the location of Nest #9, approximately 30m from the Plucking Post.

Humber Valley, Apr 7th at 11:57am. COHA (f) high in a mature maple, discovery bird giving multiple cak-series calls, attended by smaller, kik calling, adult male.

Intruder near Nest #9, Humber Valley, Apr 9th at 10:00-12:00pm. The COHA (f) is perching alone near N#9 and giving occasional (food) whaa calls. This continues until 8am when an intruder COHA (m) comes in well above the mast and from the south. He lands on the same tree as the female but (for safety?) 5m directly above her. At this moment, by direct (m/f) comparison, the new male is smaller but a similar shade of grey on the uppers and crown as the N#9 female. Also the intruder is definitely not as dark on the uppers and crown as the resident N#9 male. The intruder male has arrived without food, does several kik calls and stays put. The female stops all calls and looks straight ahead ignoring the overhead COHA (m). After 15 minutes, the intruder departs above the mast and disappears out of sight, well to the north. The female eventually resumes the whaa calls. The resident male never makes an appearance. [Other intruder behaviour in the Nest #9, Humber Valley, Apr 19th at 5:27pm and Nest #11, Col Sam Smith, Jun 4th at 10:00-1:10pm.]

Intruder near Nest #9, Humber Valley, Apr 9th at 11:23am. This male Intruder has lighter greys on the uppers & crown than the darker resident N#9 male. Also by comparison in this image, the Intruder’s left side breast is not as heavily barred as the COHA (m) in the Apr 19th image below.
Plucking Post with COHA (f) and Chipmunk near Nest #9, Humber Valley, Apr 13th at 12:23pm. Adult male delivers a Chipmunk to this Plunking Post (a large fallen tree). When the female swooped down the accept it, the male hopped 1m away. Once the female fully started tearing at the food, the male departed the Post to fetch a twig then fly to a new location (for me!): N#9.
Plucking Post, as above but better seen from a side angle, approximately 4m above grade and 30m from N#9.
At sunrise, COHA (m) dives from Nest #9, Humber Valley, Apr 15th at 6:45am. A minute earlier the female had departed. Both are nest building at dawn.
Nest #9, Humber Valley, Apr 15th at 6:55am. COHA (m/f) post-copulation, a few minutes of being close, then both start twig gathering with the female doing the nest building. By 7:30am nest activity slows, the male disappears (possibly looking for food) and the female perches near the Plucking Post with occasionally cak-series calls.

Sunset at Nest #9, Humber valley, Apr 16th at 6-8pm. Just to try something new, I went out 2-hours ahead of the 8:05pm sunset to watch how things shutdown for the evening. To my surprise at 7:05pm, I see 3-4 Eastern Phoebe approach along the westside of the valley. With frequent stops, they flew erratically between small low branches and the leaf littered forest floor. They were looking but not feeding. While still in view, these EAPH all nestled on the floor into individual dry leafy cover. At this point, the COHA (m/f) were both away but the location was below their usual perches! Other than an EAPH getting eaten, the leaf litter seemed to be a good evening roost with great thermal protection. The bonus for early-April mornings: before the leaves are out, this location gets the first direct morning sun. Finally after 7:30pm, distant COHA (m) kik-calls are heard and slowly get closer, kik calling perch by perch. He finally perches close to N#9, calls then glides into nearby deep cover. One more call at 7:50pm before silence. Over my 2-hour observation, there was no twig gathering/nest building and specifically, no COHA (f) was seen or indicative calls heard.

Sunset at Nest #9, Humber Valley, Apr 19th at 4-7pm. There are no immediate COHA sightings or calls. At 4:15pm, flying low through the trees, a Mallard (f) lands on a muddy patch 50m from N#9. There is Skunk Cabbage plus other tender greens sprouting which may be the attractant but as this duck quacks and waddles forward, the larger COHA (f) bursts in but misses her attack with the Mallard exploding away. The COHA switches to a short loosing pursuit. Soon there are distant cak-series calls. The female returns from her this pursuit and perches by the Plucking Post. The female omits low “whaa” calls (with visible jaw and tail movement). Without food, The COHA (m) returns to her position by 4:45pm. After mutual perches and calls, they copulate at 5:00pm. The male leaves shortly after and heads off at least 500m (hunting?). The female continues with whaa calls but by 5:10pm leaves with a short burst of flaps and power glide towards a distant target. Both COHA (m/f) go silent and do not return. I decide to walk towards where the female went but do not find her. Returning at 5:25pm, an intruder COHA (j) enters the N#9 immediate area. It does not call but stays close by for 15 minutes. After the juvenile’s departs, the area became fully inactive. No return appearances, etc. Over my 3-hour observation, there was no twig gathering/nest building. By 7pm, I needed a warmer jacket and welcomed the walk out.

Nest #9, Humber Valley, Apr 19th at 5:03pm. COHA (m&f) post mating, N#9, Male soon departs for possible hunt. Female whaa calls near Plucking Post, then also departs. Neither bird returns.

Intruder near Nest #9, Humber Valley, Apr 19th at 5:27pm. COHA (m/f) are gone, a juvenile was tracked perch by perch, as it silently worked in close to N#9. It then waits for 15 minutes without calling, then fully departs. The (m/f) do not return and the area has no further activity before sunset. [Other intruder behaviours: Nest #9, Humber Valley, Apr 9th at 10:00-12:00pm and Nest #11, Col Sam Smith, Jun 4th at 10:00-1:10pm.]
Nest #9, Humber Valley, Apr 24th at 1:15pm. There is no activity for my first 30 minutes watching the N#9 area and specifically I have not seen or heard the COHA (f). Suddenly the male returns with a bloody lower beak and a small dark grey headless rodent(?) in his left talons. This male gives a kik call twice with no female call back, he then takes a bite from the food. Changing perches and kik calling around the area is repeated until the food is gone. The male departs.

Egg Laying and Incubation

Mid-morning audit of Nest #6 and #8, Etobicoke Creek Ravine, Apr 28th. Both nests had the associated larger COHA (f) down inside with just the head and tail visible. The females were inactive but attentive to my presence. Each gave one soft cak-series call. The N#6 male made an appearance, not at the nest but rather to aggressively drive off a Turkey Vulture. At N#8, the male was never spotted. With significant foot traffic in the area at both nests, I limited my observation time.

Audit of Nest #9, Humber Valley, Apr 29th at 10am-12:00pm. There were full 40km winds that had everything moving. I did not hear a call or see either COHA. I spent most of the time slowing probing the territory. The clock was running down with zero results and I had to leave at Noon. At ten minutes to go, I took my final pass of N#9 as some sunlight was finally breaking through but still with the sustained winds. Viewing the nest with my 10X Binos, I noticed a white spot however, with all the moving branches, no bird. Just then I heard a soft cak-series call. The white spot was maybe wash, however it didn’t make sense that the bird would soil a nest. I pulled out my camera and used 60x with manual focus. The image below shows an egg and part of the larger hidden female. Over several images, the COHA (f) makes no effort to lie on the egg. Later with a laser range finder from my station, N#9 was confirmed at a 61m direct line-of-sight (with an estimated drop of 12-15m).

Nest #9, Humber Valley, Apr 29th at Noon, One visible egg near the belly of the COHA (f). Moments before, a low cak-series call came from N#9. The male was not seen or heard.

Nest #11, Col Sam Smith, May 1 at 2:11pm. Colonel Samual Smith Park is located between the mouths of the Etobicoke and Mimico Creeks. The outing was just a simple mid-day break to a birding hotspot during great weather. Spotted a perching Merlin (my second of the season) then closed with a COHA (f) on a new nest: N#11. Up to this point, I had not scouted COHA activity in my local Colonel Sam Smith Park (or High Park). Both are great hotspots but they are also heavily covered by many excellent Birders. By showing up on May 1st, I had missed all earlier courtship and nest building activities.

COHA (f) on Nest #11, Col Sam Smith, May 1st at 2:11pm. Located over a well used paved pathway and only 11m up. The N#11 location was know by frequent park Birders and indicative of the COHA tolerance to traffic and attention even while nesting. It was reported by others, that on May 11th, the male and female are seen together in N#11.

Nest #9, Humber Valley, May 8th at 1:20-3:00pm. After taking a scan of N#9, there is no COHA sitting on the nest. I continue to my target sitting location. Several paces before I got there, the COHA (f) gently leaves a ground level perch near my path and heads towards N#9. While I have seen her drink puddle water near by, this location is aways dry and it was not at the original Plucking Post log. I turned around and headed back to view N#9. The female was now sitting on the nest with just the backside and tail visible. Returning to my target sitting location, I now spot the COHA (m) perched 30m away. It may have been there all along, maybe a food transfer with the female before it flushed? Once I sat, the male was in a steady glare at me for 30 minutes. While there were no calls, this direct stare seem aggressive with the head frequently twitching left or right, say 30 degrees. This ended at 2:30pm, with a possible close-in behaviour, the male launched into a flight that passed 3m directly over my head. The male landed within sight on a low second perch, pooped then in plain view, flew by to one side to a third perch. This third perch was further from my location and closer to N#9. Before departing for home, I positioned to get the image of N#9 below. [Other close-in behaviour: Nest #6, Etobicoke Creek Ravine, Nest #6, Etobicoke Creek Valley, May 5th at 1:04pm and Nest #9, Humber Valley, 1:20pm.]

Female on NEST #9, Humber Valley, May 8th at 2:37pm. Briefly witnessed one egg as she repositioned in the nest. The deepest part of the bowl is not visible. N#9 looks congested with branches but there are three usable entrances.
Injured COHA (m), Col Sam Smith, May 16th at 11:58am. Possible mate to N#11 female but this male appears injured. Male reported by others to be on this recovery perch for days, 200m from N#11. Tail feathers’ barbs are messy, underbelly feathers matted but no sign of old blood. Back at N#11, upon observation the female was twice missing from the nest that morning. Female then seen perching near N#11 at 12:30pm. After a kik call, the female flew over and sat on the nest. No COHA (m) was ever seen attending her at N#11 on May 16th.

Nest #11, Col Sam Smith, May 19th at 8:30-10:00am. COHA (f) reported by others to be on nest at 7am. From 8:30-10:am, female not seen on nest or perching in the immediate area. Also, the injured COHA (m) is not found in the usual tree or on the ground near the trunk. The area from this tree back 200m to N#11 was search without success.

Dramatic dive near NEST #9, Humber Valley, May 20th at 6:45-8:00pm. At 7:00pm there are two soft distant Cak-series call getting closer from the south.  Followed by the silent COHA (m) arriving to perch midway up a tree near N#9. Not settled, the excited male jumps his way up to the upper mast then departs his high mast perch with a spectacular deep dive and hairpin u-turn back up to the next tree closer to N#9. The approaching COHA (f) is not seen but at 7:11pm, there is a cak-series call directly from N#9. I reposition and through dense foliage, take several images of N#9 with the backside/tail of the female and several white objects. 

Injured COHA (m) near Nest #11, Col Sam Smith, May 21st at 9:39am. From 7:15am on, female sitting alone on N#11, repositions every 15 minutes. By 8:35am, female is perched on the nest’s edge, when the male arrives! The smaller male sits deep in N#11. At 8:40-9:38am, female departs and takes various perches in the general area (sits on a parked van plus flies up to challenge a passing RTHA). The female eventually returns and the male departs N#9. From 9:38-9:45am, seemingly favouring one leg as in the image, the male perches before fully departing the area. [Updates on this injured male and a new intruder COHA (m), are in the paragraphs/images following: Intruder near Nest #11, Col Sam Smith, Jun 4th at 10-1:10pm below.]
In the Colonel Samual Smith Park, the period around May 14-21st represents a traumatic period for the injured male and a challenge for the success of Nest #11. In the two images above, one can see a large bare area on the lower breast (may have been plucked too), significant matting of the lower breast feathers and damage to the tail feathers’ barbs. Also in the multiple images of this male over two locations, he never stands on his right leg which is always raised up high against the bare skin.

Dramatic Dive near Nest #9, Humber Valley, May 22nd at 1:50pm. Brief walk by on a sunny crowded day. Arriving COHA (f) perches mid way up tree. Trunk is on a 10% lean, so while appearing to slip along on breast feathers, the female walk/climbs in four spurts to a higher perch. Then following a kik-call, does a deep dive and wide u-turn back up to to N#9. So both (m/f) have done this (display?) dive around N#9. The other three active nests being monitored (N#6, 8&11), are not as congested with timber and the COHA exit with more of a simple jump and when they return, tend to fly straight in with a minimal swoop up to airbrake.

Nest #9, Humber Valley, May 24th at 5:45-8:24am. Starting at sunrise, the lone COHA (f) is on the nest, adjusting position every 15 minutes. At 7:40am there is a distant soft kik cak. Following a much closer second kik call, the silent female leaves N#9 at 8:02am. After a possible food transfer, the male arrives at the nest at 8:05am. The male adjusts eggs then sits as per the 8:06am image above. The female is still gone from N#9 when I depart.
Nest #9, Humber Valley, May 26th at 7:30-10:30am. 61m view in sunny conditions with no wind. Lone COHA (f) and egg(s) in N#9 at 8:41am. No male visible but from the south at 9:20am, two distant kik calls which have no apparent effect on the sitting female.

Nest #9, Humber Valley, May 26th at 9:48am. Four Turkey Vultures soar straight by the area in close formation. There is no reaction at N#9. At 10:04am, a single TUVU returns and passes low and erratically over the mast above N#9. From an unseen perch to the south, the male charges up with full cak-series calls and twice pushes off the TUVU. [Other COHA/TUVU behaviours: Etobicoke Creek Ravine, Apr 6th at 11:55am and Nest #6, Etobicoke Creek Ravine, Apr 28th at 10:30am-12:09pm.]

Side view at 45deg below Nest #9, Humber Valley, May 27th at 7:39pm.

If Nest #6&8 both have sitting females by April 28th and with a given incubation of 34 days, hatching could happen on or before Sunday, May 31st. Further to this estimate, it takes 4 weeks of in-nest feeding before the fledge (Rosenfield 2018). On May 20th, I see my first fully fledged American Robin. It has no tail, lots of spots, can just fly and there was no attending adult. Certainly there are more prey fledglings to come. As the COHA hatch starts, the new tree leaves will provide the COHA hunting cover as it pursues easy juvenile food.

The first egg sighting in Nest #9 was from the April 29th image, with the first nestling sighting 35 days later with the June 2nd image. This small hatch date discrepancy could relate to: “The female typically begins incubation after the first 3 eggs are laid.” (Rosenfield 2018).

Nest #9, Humber Valley, Jun 1st at 7:45-10:05am. COHA (f) twice possibly listened for sounds from the eggs. First day this behaviour was witnessed (predicted hatch was on or before May 31st). At 9:41am, male arrives with a soft kik call and perches away from N#9. The female does not respond or move. Later on Jun 1st at 7:20-8:02pm, the female is sitting N#9 and eggs. No sign of hatching, calls or the male.

Nest #8, Etobicoke Creek Ravine, Jun 2nd at 9:30-10:45am. COHA (f) sitting N#8 and eggs. No sign of hatching, calls or the male. This high nest was very visible during building but now with the season’s dense leafy mast N#8 has limited viewing. Nestlings may only be visible when they have significantly grown.

COHA (f) sitting Nest #8, Etobicoke Creek Ravine, Jun 2nd at 9:59am. With all the new foliage, this view was difficult to find and was mostly obscured when the wind blew.

Nest #11, Col Sam Smith Park, Jun 2nd at 11:40-12:00pm. Only the tail of a COHA sitting N#11 was barely visible. Could have been the smaller male. No sign of hatching, calls or the other COHA. European Fire Ants swarmed my position with four stings. Time to go.

Nest #6, Etobicoke Creek Ravine, Jun 5th at 8:30-10:10am. With summer, N#6 is now partially hidden with leaves. At 8:42am, there is a distant kik call. The COHA (m) comes in to the nest with a second kik call and a small dark animal in its left claw. He passes the food to the (barely visible) female and departs to a local 14m high perch. Immediately, the male was buzzed non-stop by one then two LBJs (possibly Brown Creeper???). The COHA (m) changed perches with no relief and then left area with at least one LBJ in pursuit. At 9:20am, I depart in a wide circle to check two other N#6 viewing stations but these are now both choked with foliage.

Nest #6, Etobicoke Creek Ravine, Jun 13th at 12:00-12:57pm. COHA (f) sitting deep in N#6 with no feeding or signs of nestlings. Probably still incubating. No male was seen or heard in area. Note on nest visibility: N#6 is high in a mature tree surrounded by dense understory.  Access is now limited to a path with 3m of overgrowth while the nest has its own issues of tree foliation. Like Nest #8, N#6 became a challenge to observe anything.

New Nest #16, Withrow Park, Jun 15th at 10:15-3:08pm. Potential COHA nest information and a technical resource forwarded by Lynne Freeman (President – OFO). During an initial 2-hour scout on Jun 12th, I witnessed a COHA (f) return and sit on N#16. I returned on Jun 15th to determine if the hatch had occurred. Over this 5-hour period, the COHA (f) mostly sits on N#16 with occasional brief departures. No food is brought to the N#16 or and no nestlings are observed. The male is mostly perching nearby but never seen sitting on N#16. From observation and 175 images, there was never an indication of a nestling. The nest is probably awaiting the hatch.

COHA(f) sitting on N#16, Withrow Park, Jun 16th at 11:36am.
COHA(m) near Nest #16, Withrow Park, Jun 15th at 2:49pm.

Nest #16, Withrow Park, Jun 23rd at 9:45-11:53am. The female is mostly sitting N#16. The male occasionally lands near the nest but there is no food transfer or calls. When not at N#16, the male frequently is in a Perch Tree 30m to the SE. After a brief departure, at 10:11am, the female returns to N#16 with a large twig to modify the nest. At 10:20am, male departs north from the Perch Tree with a cak-series call. At 10:35am, there are more cak-series calls from the general north location where the male flew out of sight. At 10:45am, a RTHA is seen to the north of N#16.

COHA (m) sitting Nest #16, Withrow Park, Jun 25th at 9:20-12:24pm. Slow hot day with minor female nest building. At 12:17pm, male takes over a period of nest sitting. As the smaller bird, male generally sits lower in the nest.

Nest #16, Withrow Park, Jun 27th at 9:45-1:00pm. Slow hot day with little activity. Female mostly sitting N#16.

Nest #16, Withrow Park, Jun 29th at 9:20-11:00am. Slow hot day with little activity. Female mostly sitting N#16.

The Hatch and Nestlings

Nest #9, Humber Valley, Jun 2nd at 2:37-3:37pm. A silent COHA (f) is sitting N#9. At 2:45pm, a distant kik call. The female departs the nest. At 2:47pm, a distant/low cal-series call. By 2:49pm, the male arrives and soon sits on N#9. At 3:22pm, a distant kik call and then after distant/low cak-series call, the male departs, then two more distant kik calls. At 3:24pm, the female arrives, stands on N#9, with a final distant kik call. She soon starts tearing at the fleshy food she has brought. The female is clearly feeding small morsels from her beak to a single nestling (as per the image above, the blue arrow points to the downy white head of the first-day nestling while the two red arrows indicate unhatched eggs). Feeding stops at 3:32pm when the female sits on N#9. The estimated date for the N#9 first hatch: June 2nd.
Nest #9, Humber Valley, Jun 4th at 8:45-9:07am. COHA (f) and heads of two nestlings.

Intruder near Nest #11, Col Sam Smith, Jun 4th at 10:00-1:10pm. COHA (f) sitting on the nest and adjusting position every 15 minutes. No sighting of the injured male. At 10:18am, female has a small poop off the nest edge. There are several small washes around the outer nest which may indicate the female is not eating much and is hesitant to leave the nest. The smallest of these washes could also be from new nestlings as per: “…young squirt their white feces over the nest rim…”. (Rosenfield 2018). At 12:00pm, the female is still sitting N#11 when an intruder COHA (m) perches on several branches and the ground, 15m away. At 12:15pm, this new male gives a kik call and goes directly to the nest’s edge. After a brief stay (and probable food delivery), the male gives a second kik call then departs to a local perch. The female is still in N#11 but now stands, continuously with her head down for 20 minutes, seemingly feeds a nestling(s). [Other intruder behaviours: Nest #9, Apr 9th at 10:00-12:00pm, Humber River and Nest #9, Humber Valley, Apr 19th at 5:27pm.]

COHA (f) with food in feeding position, Nest #11, Col Sam Smith, Jun 4th at 12:31pm. For 20 minutes, female stands with head down to pluck at food and bobs to seemingly feed a nestling(s). Also in this image, there are visible spots of small washes around the outer nest. Small spots of wash are also on the nest’s opposite side.
Intruder COHA (m) near Nest #11, Col Sam Smith, Jun 4th at 12:00-1:10pm. Orange eyes vs. yellow with injured male, no damage to tail barbs, uses both feet to perch and is not missing belly feathers. This male is very assertive in the area. It was reported by others that on Jun 3rd, that a new COHA (m) was seen copulating with the female near N#11.
Potential food cache near Nest #11, Col Sam Smith, June 4th at 1:00pm. A very immobile Black Squirrel located at the same 9m elevation and 8m from the perching intruder COHA (m). These larger aggressive mammals mostly ignore the threat of COHA.

Nest #11, Col Sam Smith, Jun 5th at 10:26-12:23pm. A COHA (f) tail was visible in N#11 and the squirrel cache was gone. At 10:30am, there is a distant kik call, then the intruder male arrived (carrying a small rat) at a local secluded perch. The male did two whaa calls from the perch. The female in N#11 gets active then at 10:36am, departs to male’s perch. At 10:38am, with a kik call and no food, the intruder male lands then hops into N#11. At 10:42am, the restless female returns to stand at the edge of N#11 while the Intruder male continues to sit. At 10:44am, the intruder male fully departs N#11, follow by the female. At 10:52am, the original injured COHA (m) comes in to perch near N#11. Soon the injured male moves to a second perch nearer N#11. The other two adults are still gone and he is silent. At 11:00am, the injured male lands on N#11 then sit in the nest! By my departure at 12:23pm, the injured male/assume parent, is still sitting and the two other adults have not returned. With two males and one female attending N#11 on Jun 5th, it would be interesting to document any future repeat of this social system.

Injured COHA (m) near Nest #11, Col Sam Smith, Jun 5th at 10:57am. Feathers are matted & ratty with the adult breast colouration almost masked. There is still a bald breast area but he is now using his right leg.

Nest #11, Col Sam Smith, Jun 8th at 9:44-12:14pm. Intruder COHA (m) is sitting N#11 with the female perched near by. Several times Black/Grey Squirrels and Common Grackle get within 2-3m of N#11. At 11:16am, intruder male leaves nest to perch nearby. At 11:19am, female arrives at N#11 with a large twig. From his nearby perch, intruder male returns (without food) and perches on N#11. This male soon leaves area. Female stays sitting N#11 until my departure. The injured male was not seen in the above sequence.

Four nestlings in Nest #9, Jun 8th at 6:45-7:00pm, Humber Valley. Female feeds meat to brood.

Nest #11, Col Sam Smith, Jun 10th at 11:45-3:09pm. COHA (f) sitting N#11, intruder male perched nearby. At 12:47pm, a restless female departs N#11 then returns at 12:53pm to sit N#11. Following a quick nest visit by the intruder male, at 12:56pm the female stands and starts a brief feeding of at least two (witnessed) nestlings. Meanwhile, intruder male twice comes/goes from N#11. After two nearby kik-calls from perching area, at 3:02pm the female leaves N#11 toward calls and quickly returns with small bird. She stands and feeds nestlings till my 3:09pm depart. The injured male was not seen in the above sequence.

Grey Squirrel at Nest #11, Col Sam Smith, Jun 10th at 1:23pm. Nearby squirrels are frequently passing through the mast but this squirrel appeared to be testing the boundaries. When squirrel got above the N#11 sightline, the female flared its wings (see wing tip on right) and the squirrel raced up and away.
Nest #9, Humber Valley, Jun 11th at 4:30-5:15pm. Image of four nestlings just after feeding and COHA (f) about to depart. The nestlings generally hatched starting on June 2nd and in this image, are 9-6 days old. Note that a head count of nestlings at this stage is a challenge with their small downy wings being flexed upwards. A tight sequence of images helps to sort the count out.

Nest #11, Col Sam Smith, Jun 13th at 1:30-4:26pm. Over this 3-hour period, the COHA (f) was sitting N#11 with several departures to/from local perches. This includes a 2:34pm return with a small twig. Also, at 3:02pm from the secluded Plucking Post, the intruder male gave a kik call then double whaa call for a food transfer. At 3:03pm, female departs to this overgrown and secretive Plucking Post. The female soon returns to N#11 with a small bird and feeds two (witnessed) nestlings. During the same 3-hour period, the intruder male was mostly perching nearby in several locations and on the ground twice. The injured male was not seen.

New Nest #15, Prospect Cemetery, Jun 14th at 12:40-3:00pm. Information from Rob & Christine Elliott, on a new COHA nest was forwarded by Mark Lichtenberg (Member – TOC). As my first time scout at this location, I examined each potential nesting tree. At 1:00pm, there was a COHA (m) in a low flyby, ending in a perch. The next focus was on where this bird had came from (found nothing). Returned to the perched male which was still staring at a stand of mature trees 100m west. At 1:38pm, I depart towards these mature trees. At 1:40pm, male also departs in this direction while from the south, a larger COHA (f) now heads through these same trees to intersect the male. At 1:45pm, the female departs the stand of mature trees and lands on the Perch Tree where the male had been watching from. Once perched, the female has a poop. After continuing the search, at 2:04pm, sighted the unattended COHA N#15.

Perch Tree, Prospect Cemetery, Jun 14th at 1:00-1:40pm. COHA (m) is continually staring in one direction (Nest #15).
COHA (f) on Perch Tree, Prospect Cemetery, Jun 14th at 1:45-2:13pm.
Prospect Cemetery, Jun 14th at 2:02pm. Looking north, left arrow: Nest #15 at 15m above grade. Center arrow: Plucking Post. Right arrow: Perching Tree (and secondary Plucking Post) 85m from N#15. Also had COHA (f) undisturbed on a low perch as two visitors worked below.
Plucking Post, Prospect Cemetery, Jun 14th at 2:14-2:24pm. Incoming male with food and a kik call, lands on the Plucking Post. Female launches from Perching Tree, twice whaa calls in flight, then aggressively lands into a suddenly departing male. The food is a nestling prey with pin features and greyish down, which she actively plucks but does not consume. Once prepared, female departs for N#15.
Nest #15, Prospect Cemetery, Jun 14th at 2:24-2:40pm. Female tears at food and feeds the nestlings which appear as small white downy shapes around her. As in this image, once feeding was over, the female moved forward to depart.
Nest #15, Prospect Cemetery, Jun 14th at 2:40-2:45pm. Now with more room in N#15, three nestlings move up the edge for a view out.
Nest #15, Prospect Cemetery, Jun 14th at 2:46pm. The nestlings soon settle down with a final wing stretch. Nestling’s dark pin feathers with white down indicates 14 days after hatch (Madden 2018).
COHA (f) left of four nestlings in Nest #9, Humber Valley, Jun 18th at 2:45-4:11pm. Despite being 61m out, N#9 has been a very productive site for observing and photographing COHA nesting activity in a secluded high-mast environment. However, the seasonal budding and tree growth has eliminated several vantage points. Now the best viewing station is being blocked as growing cones sag down.

Nest #15, Prospect Cemetery, Jun 19th 10:15-11:11am. At 10:19am, COHA (m) gives two kik calls from the distant Perch Tree. Female then leaves perch near N#15 to displace male as she apparently takes food. With multiple whaa calls, the female starts plucking food at the Perching Tree. At 10:24am as the female continues to pluck, the male returns and copulates with her.

Nest #15, Prospect Cemetery, Jun 19th 10:39am. Now it’s four nestlings, who are very active after a 10:28-10:33am feeding from COHA (f). From left to right, these juvenile’s colouration indicates 18 (J#2), 19 (J#1), 17 (J#3) & 16 (J#4) days after hatch (Madden 2018). Note the the two nestlings on the left appear to be fully standing while the two on the right are probably squatting at the back of N#15. The estimated date for the N#15 first hatch: May 31st.

Nest #11, Col Sam Smith, Jun 20th at 9:30-11:40am. COHA (f) mostly attends N#11 from nearby perch. After occasional kik calls, at 10:00am the intruder male arrives and sits in N#11 for 5 minutes then departs. Over the observation period, there is no injured male and no transfer of food or feeding at N#11 but for the first time, four nestlings are now visible.

Nest #9, Humber Valley, Jun 21st at 9:30-11:00am. Scouting failed to produce good alternative vantage points, however some views included a new Perching Tree/Plucking Post (horizontal branch). As witnessed at 10:00-10:20am, COHA (m) with a small prey bird, arrives at Perching Tree, gives two separate kik calls, female arrives from N#9 area, accepts food and plucks food before returning to N#9 to feed nestlings.

Nest #16, Withrow Park, Jun 30th at 1:30-3:37pm. Slow hot day with little activity, Female mostly sitting N#16. Watching for hatch including with a 45x spotting scope. Nothing conclusive with the camera but through the scope, the COHA (f) stands in N#16 with her head well down for a few minutes. This was repeated twice in one hour. Note that there was no clear inverted “U” motion of plucking up with a food morsel then a move to the side and down to a waiting nestling. However, the female’s head was fully active with something out of sight in the nest. My observations were weak as stand-alone proof of the N#16 hatch but it definitely supported the two nestling confirming observation, on Jul 1st by Lynne Freeman (with spotting scope). From this, the working date for the first hatch is Jun 29th and is supported by a same-day observation by Stephanie Birkett (Member – TOC). 

Tree Base of Nest #16, Withrow Park, Jul 2nd. Stephanie Birkett finds the larger of two egg shell fragments, pale bluish white, width 39mm. On Jul 4th, SB finds a dead COHA nestling at the same base.
Nest #16, Withrow Park, Jul 6th at 9:30-11:40am. Observation starts with the COHA (f) sitting the nest with little activity for over 90 minutes. The male flies past but later returns at 11:16am to the Perch Tree. After the male gives two kik calls, the female leaves N#16 for a food transfer & pluck. N#16 becomes active as the female returns and primarily feeds the visible three nestlings (with occasional morsels for herself) from 11:23-11:36am. The image above is at 11:33am and shows three nestlings (red arrow) below the female. From left to right, these juvenile nestlings are J#1, J#2 and J#3 (J#4 is a presumed fatality, mentioned above). From a steam of camera images, J#1 has the highest reach when feeding, is fed most often and frequently grabs at food held by the slightly smaller J#2. J#1 was never seen to injure the others. J#3 is the smallest juvenile and was rarely seen above the nest line. From earlier observation, it is estimated that these juveniles are 5-7 days after hatch. The estimated date for the N#16 first hatch: Jun 29th. This is much later than the two other noted first hatch dates: Nest #15 on May 31st and Nest #9 on Jun 2nd.

Fledging, the final observations

Nest #15, Prospect Cemetery, Jun 26th at 10:45-12:30pm. Three nestlings (J#2, 3 &4) remain in N#15. At 11:27am the COHA (f) with 3 kik calls, moves from an adjacent tree to the primary Plucking Post. At 11:29am the male arrives at Plucking Post to transfer food then quickly departs. Female does whaa calls and starts plucking a House Sparrow. At 11:38am, after two more whaa calls, the female goes to N#15. By 11:48am, feeding these three nestlings is over.
Nest #15, Prospect Cemetery, Jun 26th at 12:01pm. The second largest juvenile (J#2) with colouration indicating 24 days after hatch (Madden 2018). The largest fledging juvenile (J#1) is off-camera in an adjacent tree and did not join the feeding in N#15. It was possibly fed separately.
Nest #15, Prospect Cemetery, Jun28th at 10:30-12:42pm. At 10:41am, J#4 is low in N#15 while J#3 was about to jump up/out 50cm to branch. J#3 has a colouration indicating 26 days after hatch (Madden 2018). J#1 and J#2 are perched in other nearby trees.
Juvenile #2, 10m from Nest #15, Prospect Cemetery, Jun 28th at 10:47am.  J#2 has colouration (and remaining down on crown) indicating 27 days after hatch (Madden 2018).
Nest #15, Prospect Cemetery, Jun 28th at 10:52am. The nest area is active with the two youngest juveniles swapping positions on nearby branches especially after 10:47am when the female arrived at the Plucking Post. Here, J#4 has a colouration indicating 25 days after hatch (Madden 2018).
Nest #15, Prospect Cemetery, Jun 28th at 10:56-11:03am. COHA (f) feeding a quick rotation of all juveniles at N#15. At 11:59am, J#1, which is taking the above food, has colouration indicating 28 days after hatch (Madden 2018). At 12:25pm, J#1 is perching 30m west of N#15.
Plucking Post near Nest #15, Prospect Cemetery, Jun 28th at 10:51am. In a typical shady spot below the Plucking Post, my station had a good view into N#15 along with a chair and camera tripod (blue arrow). After an exchange of calls, the female and male meet at the distant Perch Tree, then the female flies back with food to my visible location to start plucking directly overhead (red arrow). The Plucking Post was a mature Beech with several sturdy horizontal branches that have all been used for plucking, but today literally over my head was the COHA choice (possible close-in behaviour). No poop was discharged but after taking the above photo, the chair was adjusted just in case! [Other close-in behaviours: Nest #6, Etobicoke Creek Ravine, Apr 12th at 10:22am, Nest #6, Etobicoke Creek Ravine, May 5th at 1:04pm and Nest #9, Humber Valley, May 8th at 1:20pm.]
Nest #15, Prospect Cemetery, Jul 1st at 2:15-4:22pm. Sunny hot day with N#15 initially empty, then later, random single-juvenile visits. At 2:33pm, the COHA (f) silently arrives from afar with a small bird and feeds the one juvenile in N#15. As in the above image, at 2:41pm the female departs, with half the bird carcass, and disappears 40m north of the distant Perch Tree. During the entire observation period there were no calls or other flybys.

Nest #15, Prospect Cemetery, Jul 3rd at 1:00-2:37pm. Sunny hot day, N#15 was empty of juveniles, with no calls or local perching or flybys for the first hour. Then at 1:57pm, the COHA (m) arrives at the Plucking Post. There is a quick exchange of calls as the female arrives for a food transfer. By 2:01pm, numerous fledgling speeeeeeeeo calls (almost a whistle) emanated from local trees masts and the female lands at N#15 delivering an un-plucked small prey bird. This starts a rotation of 1-2 juveniles in/out of N#15. As they continue the speeeeeeeeo calls, one juvenile at a time, plucks/feeds. At 2:04pm, the female departs to the Plucking Post and perches to watch the noisy commotion at N#15. By 2:33pm, N#15 is mostly quiet and the female departs the Plucking Post. At 2:37pm, N#15 has one small juvenile perched on the edge.

Nest #15, Prospect Cemetery, Jul 3rd at 2:21pm. Juvenile learning to self-feed. Temporarily had a possible bird leg, stuck in its throat.

Nest #15, Prospect Cemetery, Jul 8th at 10:30-12:30pm. Two COHA (j) are in the area but not holding in N#15. As a pair, they frequently change perches but mostly stay within sight of N#15, the Perch Tree and each other. The juveniles have the ability to quickly walk lengths of tree branches. Also in one case, a juvenile lay lengthwise on a branch as the other juvenile stood nearby. Over the observation period, the COHA (m) comes in silently three times to provide mostly intact prey birds, twice at the Plucking Post and the third time was at the N#15 itself. There is little adult interaction, mostly a brief turn around. The juveniles would immediately spot this food drop-off, break into fledgling speeeeeeeeo calls, then fly closer to the food to individually pluck/feed (read: one at a time, no competing or fighting). Again over this observation period, the COHA (f) and the other two juveniles were not seen.

Plucking Post near Nest #15, Prospect Cemetery, Jul 8th at 12:19pm. Two COHA (j) take full notice of a Great Crested Flycatcher’s weep calls from the adjacent mast. Individually, the two juveniles’ colours vary from a sharp dark streaking on a white chest, to the other with a more rufous chest. Finally, these juveniles still had blue-green eyes. Using May 31st as the first juvenile’s date of hatch, on Jul 8th, all four juveniles would be 38 days or less, after the hatch. This fits with the timing of 39+ days after the hatch for COHA eye colour to change from blue-green to yellow (Madden 2018).
Prey remnant below Plucking Post, Prospect Cemetery, Jul 8th at 12:26pm. Given size, colouration and the unique plucked flight feathers nearby, possible juvenile European Starling. The ground around N#15 had signature COHA litter: molted adult COHA tail & flight feathers, juvenile poop and debris from prey plucking.

Nest #15, Prospect Cemetery, Jul 8th at 10:00-11:50am. The observation started with no visible nearby COHA juvenile activity or perching. At 10:35am, a juvenile was spotted 30m away, on a walkway drinking from pooled sprinkler water. It immediately departed for the Plucking Tree, then departed again, to hide in the highest level of a dense mature Willow. While it was not pushed, it seemed spooked as if from a previous encounter. At 11:28am, the COHA (m) silently goes into N#15 for an unplucked prey drop, then departs. With ongoing speeeeeeeeo calls, the juveniles converge on N#15. While one juvenile at a time would pluck/eat in N#15, for the first time with two separate birds, there was mantling over the food. At 11:48am, the feeding on N#15 was over. Note that besides the COHA (m), there was three confirmed juveniles. However, with the shuffling from secluded perches, a fourth (unconfirmed) juvenile may have been in the mix.

Nest #11, Col Sam Smith, Jul 12th at 11:00-12:08pm. Upon arrival, N#11 is empty with one large juvenile perched high in the open, 75m to the west. Without observing the actual adult food drop, at 11:27am a second juvenile appeared at N#11 to pluck/eat a prey bird. At 11:40am, a third juvenile came in with a single speeeeeeeeo call and landed past N#11. This third juvenile, actively hopped through the upper branch tangle to get into a position just above the feeding second juvenile in N#11. At 12:03pm, the second juvenile is displaced and the third juvenile mantled over the food, before it fed. While only three juveniles were witnessed during this period, it was reported by others, that four juveniles were still using N#11 for feeding and have recently been seen in a loose group. 

Nest #11, Col Sam Smith, Jul 12th at 11:50am. Third juvenile was working through Spruce clutter to find a favourable angle down to displace the feeding second juvenile on N#11. With both the current N#11 and Jul 8th N#15, the juveniles have noticeable mass and possibly are starting to show a size difference between the sexes. Definitely around both N#11 and N#15, the juveniles are well into fledging and are starting to scatter.

Nest #9, Humber Ravine, Jul 12th at 8:00pm. This was a chance drop in to view any N#9 evening activity. The view was heavily obscured by growth with nothing visible to witness.

Comments on my COHA Birding Plans

  1. My first-time focus on a single species was a rewarding challenge. I would recommend it to others. The species and duration is up to the Birder.
  2. An early review of species specific reference material is helpful.
  3. From my 2020 effort, I now have six active COHA sites (Nests #6, 8, 9, 11, 15 & 16). Five of six nests are within 7km of my Etobicoke home. Multiple nest sites were helpful over the duration given potential nest abandonment and seasonal tree budding eliminating good views.
  4. Mating is a noisy time from COHA calls, once the nested pair is established, call frequency and volumes typically drops. However, some nests (N#11 & 15) remain relatively loud, while some get very quiet, almost secretive (N#6 & 9).
  5. The scouting of the Mimico Creek Ravine was thorough but an active nest was not sighted. I had a bias to focus literally on Mimico’s narrow ravine structure while not putting enough time on the adjoining residential neighbourhoods which have plenty of mature trees to nest in. Around my home, Red-tailed Hawk, Merlin and American Crow are nesting in backyard trees. There is probably a COHA nest in the neighbourhood too.
  6. During the upcoming Winter 20/21, I may track my local overwintering COHA. Could there be a subgroup that migrate south (say from as far north as Lake Timiskaming) but hold over in the Toronto region? I would appreciate any communication or previous COHA Migration studies on this.

Reference Material Used

Cornell Lab of Ornithology. 2020. Birds of the World (Cooper’s Hawk) website.

Dunne, P., 2017. Birds of Prey. Houghton Mifflin Harcourt, Boston MA, 305pp.

Madden, K., 2018. A Photographic Guide For Aging Nestling Cooper’s Hawks. U.S. Fish & Wildlife Service

Rosenfield, R.N. 2018. The Cooper’s Hawk. Hancock House Publishers, Surrey BC Canada, 163pp.


Freeman, L. 2020. Comments over several emails.

Maione, I. 2020. Comments over several emails and texts.

Rosenfield, R.N. 2020. Questions and comments over several emails.

Photo Credit

Roberts, B. All photos

After 6 months of COHA observations and blogging 10,000 words,

it’s time to call it…

The End


Failed Nest #16, Withrow Park, Jul 31st at 12:15-12:48pm. Empty nest with no sign of juveniles or adult COHA. From personal observations and the reports of others: Jul 4th: J#4 found dead at N#16 tree base (few days from hatch, not eaten). Jul 17th: J#3 now missing from nest. Jul 25th: Adult female found dead at tree base (partially plucked and eaten), adult male feeding the two surviving juveniles. Jul 30th: J#2 found dead in branches 2m above ground (partially eaten and head missing), adult male was still dropping food at N#16. Jul 31st: J#1 found dead at N#16 tree base (numerous plucked juvenile feathers scattered about, heavily eaten and head missing), no sign of attending adult male. Aug 4th: Adult male most likely seen, then reported by email (along with a good phone image). It was perching (as usual for the male) over the dog park, north of N#16 and inside the nest territory. Finally during the above month of activity, there was never a witnessed or reported predation during daylight.