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.
Regards,
Julian Julian Hough New Haven, CT 06519 www.naturescapeimages.wordpress.com
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@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.
Regards,
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
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.
Steve MayoBethany
From: julian hough via CTBirds <ctbirds@lists.ctbirding.org>
To: "ctbirds@lists.ctbirding.org" ctbirds@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.
Regards,
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
A 1984 article on the results of banding over 1000 Northern Harriers at several North American locations in the fall migration has some relevant data.
The order of average fall migration appears to be young male, young female, adult female, and, last, adult male, with much overlap in dates.
The authors of the study found only about 10% of their caught birds to be adults, with slightly more female adults (and slightly more male young birds). Thus, "gray ghost" adult males were only about 4% of the total. The authors caution that there may be sex and age biases in the capture techniques, so the data on captured and banded birds might not be fully representative of the population.
I am not aware of sex or age differences in non-breeding habitat or latitudinal range for this species, but it wouldn't surprise me if there were such differences, which could affect proportions of encounters with adult males in any given area.
The article is
Keith L. Bildstein, William S. Clark, David L. Evans, Marshall Field, Len Soucy, Ed Henckel. 1984. Sex and Age Differences in Fall Migration of Northern Harriers. Journal of Field Ornithology 55:143-150.
You can get a PDF of the article from SORA at https://sora.unm.edu/node/51088 .
By the way, does anyone know who first used "gray ghost" for male N. Harriers? My impression is that it is a relatively recently coined term.
David
David Spector
Belchertown, Massachusetts
From: CTBirds [ctbirds-bounces@lists.ctbirding.org] On Behalf Of Arthur Shippee via CTBirds [ctbirds@lists.ctbirding.org]
Sent: Monday, December 28, 2015 3:16 PM
To: Birds General reports
Subject: Re: [CT Birds] Gray Ghost - a skewed perception?
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@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.
Regards,
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
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
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@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.
Steve MayoBethany
From: julian hough via CTBirds <ctbirds@lists.ctbirding.org>
To: "ctbirds@lists.ctbirding.org" ctbirds@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.
Regards,
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
From my field notes from several years of birding inland in Storrs, i have recorded a proponderance of adult males in late May and early June as well as late in the fall migration season, even approaching Christmas count time.
This would correspond to adult males being the later migrants. Also, the ratio of adult males to other plumages from my sightings at these inland locations in closer to 50/50. These are not hawk watching numbers but more coincidental sightings in this largely mixed forest and agricultural field habitat
The number of adult males compared to other plumages i have seen up here is actually rather surprising to me.
Mark.
Mark Szantyr
On Dec 28, 2015, at 4:37 PM, Spector, David (Biology) via CTBirds ctbirds@lists.ctbirding.org wrote:
A 1984 article on the results of banding over 1000 Northern Harriers at several North American locations in the fall migration has some relevant data.
The order of average fall migration appears to be young male, young female, adult female, and, last, adult male, with much overlap in dates.
The authors of the study found only about 10% of their caught birds to be adults, with slightly more female adults (and slightly more male young birds). Thus, "gray ghost" adult males were only about 4% of the total. The authors caution that there may be sex and age biases in the capture techniques, so the data on captured and banded birds might not be fully representative of the population.
I am not aware of sex or age differences in non-breeding habitat or latitudinal range for this species, but it wouldn't surprise me if there were such differences, which could affect proportions of encounters with adult males in any given area.
The article is
Keith L. Bildstein, William S. Clark, David L. Evans, Marshall Field, Len Soucy, Ed Henckel. 1984. Sex and Age Differences in Fall Migration of Northern Harriers. Journal of Field Ornithology 55:143-150.
You can get a PDF of the article from SORA at https://sora.unm.edu/node/51088 .
By the way, does anyone know who first used "gray ghost" for male N. Harriers? My impression is that it is a relatively recently coined term.
David
David Spector
Belchertown, Massachusetts
From: CTBirds [ctbirds-bounces@lists.ctbirding.org] On Behalf Of Arthur Shippee via CTBirds [ctbirds@lists.ctbirding.org]
Sent: Monday, December 28, 2015 3:16 PM
To: Birds General reports
Subject: Re: [CT Birds] Gray Ghost - a skewed perception?
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@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.
Regards,
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
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
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