[CT Birds] Gray Ghost - a skewed perception?
ashippee at snet.net
Mon Dec 28 15:16:14 EST 2015
Do we know if migration patterns are similar for M and F Harriers? Might there be different routes, or days, or times during the day? Different migration patterns would likely produce different observational patterns.
Thanks for the discussion.
> On Dec 28, 2015, at 12:52 PM, julian hough via CTBirds <ctbirds at lists.ctbirding.org> wrote:
> 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
> This list is provided by the Connecticut Ornithological Association (COA) for the discussion of birds and birding in Connecticut.
> For subscription information visit http://lists.ctbirding.org/mailman/listinfo/ctbirds_lists.ctbirding.org
More information about the CTBirds