[CT Birds] Gray Ghost - a skewed perception?
jrhough1 at snet.net
Mon Dec 28 16:39:26 EST 2015
To quote Steve, "I'd bet the numbers for both confirmed adult male and female NHs, would be relatively small."
I don't think Steve meant to include adult males in his comment, since the main point I was making was that confirming the number of adult males should be easy - being uniquely grey and ghost like!It is the adult females that need scrutiny to age/sex being basically close to the juveniles in appearance.
Also, someone in a personal email to me remarked that nearly 50% of inland harriers he sees in winter are adult males, so there may also be a geographical bias to the numbers when you consider how common one age class/sex is at a particular watchpoint???
Julian Hough New Haven, CT 06519 www.naturescapeimages.wordpress.com
On Monday, December 28, 2015 4:19 PM, Steve Mayo and Rebecca Horowitz <rsdmayo at sbcglobal.net> wrote:
Well, in spite at my feeble attempt a joke, I knew that just being polygynous (the males apparently dying off because of the psychological stress of having several mates) wasn't the answer.
At Lighthouse, on November 14, 2015, there were 33 Gray Ghosts among a total of 63 NHs. Quite a day. Conversely, in all of September there were 62 total NHs. I wouldn't be surprised if not a single one was a Gray Ghost.
We could definitely do a better job aging and sexing these birds, especially on the increasingly common slow days at Lighthouse. I'd bet the numbers for both confirmed adult male and female NHs, would be relatively small. Numbers would be low for other late-season adult migrants such as Sharp-sinned and Coopers Hawks as well.
Thanks for the comments Julian, I think you're spot-on.
From: julian hough via CTBirds <ctbirds at lists.ctbirding.org>
To: "ctbirds at lists.ctbirding.org" <ctbirds at lists.ctbirding.org>
Sent: Monday, December 28, 2015 12:52 PM
Subject: [CT Birds] Gray Ghost - a skewed perception?
I don't have access to Lighthouse data, so this is purely based from the hip, on what I see at Lighthouse. Adult harriers of both sexes, like accipiters, come through at the tail end of the season. During the mid-season (say mid-Sept to mid-October) the bulk (90%) of the birds are juveniles. I don't see many adult females going through at this time. When I analyzed the sexual make-up of a small sample of banded juveniles for some research I was doing on Northern Harriers, or sexed the birds passing lighthouse by eye-color (gray-olive on males, dark brown on females), I found that juvenile females were outnumbered by juvenile males. So, hypothetically, if a nest contained generally more young males than females, in two years' time, adult males should make up a larger percentage of the harrier population.
But...I feel the suggestion that adult male "Grey Ghosts (awesome name by the way!!!) are less common, is down to a misconception. Again, all this is unscientific, since in fall, unsexed and unaged "brown" birds (young males, young females and adult females combined) obviously outnumber "gray" birds so it may be a skewed perception of the observer since they are seeing a much higher percentage of "brown" birds compared to a single age/sex class of a "gray" birds.
I think the original comment may have assumed all the "brown" birds in fall are females. The key would be to compare the numbers of only adult females with "Gray Ghosts" to get a better feel of the numbers and this would require good views to differentiate adult females from juveniles in fall.
Julian Julian Hough New Haven, CT 06519 www.naturescapeimages.wordpress.com
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