Kestrel Week III

Headless Kestrel on Rooftop Bar! They absolutely love old school TV antennas, which still litter the rooftops of Brooklyn, thank goodness. And strange pipes shooting up from rooftops. This is a rare neighborhood appearance by a female. There is no slate blue on her wings and she has more subdued head-patterning. She also doesn’t have the wide black terminal band on her tail that distinguishes the male in flight overhead. As I noted earlier, these little falcons make a lot of noise. She was calling loudly here.

From the literature: The Wilson Journal of Ornithology Vol. 121, No. 1 (Mar., 2009), pp. 12-21, reports that mate and nest site fidelity for the species in southwestern Idaho is rather loose. “Seventy-seven percent of boxes had different males and 87% had different females where nest-box occupants were identified in consecutive years. High turnover rates were partly a result of box-switching. Forty-eight percent of males and 58% of females that nested within the study area in successive years used different boxes.”

“Kestrels that switched mates and boxes did not improve or decrease their subsequent nesting success.”

“The costs of switching boxes and mates were low, and there were no obvious benefits to fidelity. The cost of “waiting” for a previous mate that might have died could be high in species with high annual mortality.”

Some more information on breeding, from Weidesnsaul’s Raptor Almanac: normal clutch size 4-5 eggs, with a range from 3-5; incubation period 27-31 days; nestling period 28-31 days. Average length of dependence on parents, egg-laying to dispersal, is 80 days; compare to 140 days for Red-tailed Hawk.

Weidensaul also notes that Kestrel egg weight as a percentage of female’s body weight is a whopping 11.4%, the highest proportion of the 27 species he notes. For a Bald Eagle, it is 2.3%. American Kestrel is the smallest species on Weidensaul’s list. Other small species, like the Sharp-shinned Hawk (10.7%), Eurasian Hobby (10.4%), and Eurasian Kestrel (9.5%) show this is very much about the size of the bird.Two local males looking peaceful, but they do chase each other around otherwise.

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I cobbled this together for my birthday a few years ago.

7 Responses to “Kestrel Week III”


  1. 1 nature969 February 20, 2018 at 7:44 am

    Happy birthday, matthewwills! I enjoy your blog and wonderful information and photos. My granddaughter is one today. The birds are singing in the tress around us welcoming the season. To quote another Beatles’ song, “ooh blah dee, ooh blah dah, life goes on by”
    Have a great day and thanks again for your blog!
    – Janine

  2. 3 Peggy Herron February 20, 2018 at 8:51 am

    Kestrels are one of my favorite hawks. Thank you for the breeding info .
    Happy Birthday

  3. 5 alaspooryorick February 20, 2018 at 2:42 pm

    thanks for taking me birding with you. Happy B-day.


  1. 1 Kestrel Check-In | Backyard and Beyond Trackback on March 17, 2018 at 8:01 am

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