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.
Cannibalizing Old Nest Material
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:
- 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.
- 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.
- GHOW breed mid-winter and don’t seem the fit the timeline of this nest cannibalization except for maybe N#1.
- 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.
- 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.
- 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.
- 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.
- Walk slowly towards any distant call or low-overflight. Check horizontal branches of larger trees. Frequent stops, can be very productive.
- 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.
- 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?
- 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.
- 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.
- 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).
- 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: https://brbirding.wordpress.com/winter-birding-in-toronto-2020/.
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!
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:
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.
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.
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.
Nest #8 in the Etobicoke Creek Ravine
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.
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.]
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 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 #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.
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.]
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.
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 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.]
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 #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.
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.
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.
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
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.]
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.
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.
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.
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 #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).
Fledging, the final observations
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 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.
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 #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
- 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.
- An early review of species specific reference material is helpful.
- 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.
- 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).
- 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.
- 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. https://birdsoftheworld.org/bow/species/coohaw/cur/introduction
Dunne, P., et.al. 2017. Birds of Prey. Houghton Mifflin Harcourt, Boston MA, 305pp.
Madden, K., et.al. 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.
Roberts, B. All photos
After 6 months of COHA observations and blogging 10,000 words,
it’s time to call it…
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.