BirdsDK: Sørgedue Zenaida macroura, 20.5.2008, Skagen

onsdag den 21. maj 2008

Sørgedue Zenaida macroura, 20.5.2008, Skagen

Sørgedue Zenaida macroura, 20.5.2008, Skagen

Sørgedue Zenaida macroura, 20.5.2008, Skagen, bemærk svagt iridiserende grønt og pink på øredækfjer

Sørgedue Zenaida macroura, 20.5.2008, Skagen, bemærk hvidt på de tre yderste halefjer i hver side foruden relativt korte centrale halefjer

Nedenstående blev sendt i personlige mails til flere bidragsydere, som venligst kommenterede på en kort forespørgsel på ID Frontiers:

Hi,

I hope you have time for a few comments on a Morning Dove found in Denmark in Scandinavia.

Photos from different angles can be viewed here and here, just click the photos and the will enlarge for you.

If accepted as a potential spontaneous record, it constitutes the first ever record for Scandinavia accepted in category A.

The big question for the Danish and other Scandinavian birders is now whether the photos support a determination of subspecies as well as age class?

I have several questions that European birders can’t answer

Subspecies: Are the exposed primaries and wings in general long enough for the bird to be either an Eastern mourning dove (Z. m. carolinensis) or a Western mourning dove (Z. m. marginella)? Can we exclude the more southern subspecies by the length of primary projection? Is the plumage in general pale enough for the bird to be an Eastern mourning dove (Z. m. carolinensis)? (source: Birds of North America (BNA 117, 1994) and http://www.birds.cornell.edu).

Sex: Does the fact that the there are extensive white tips the three outer tail feathers in each tail side suggest a male? Does the fact that the bare skin around eyes is turquoise blue suggesting male? (source: Birds of North America (BNA 117, 1994) and http://www.birds.cornell.edu).

Age: Does the fact that the central tail feathers are relative short compared with other tail feathers indicate a 2.nd calendar year age class? Is it true that the gap is vinaceous in immature birds and vinaceous to deep vinaceous in adults, and what does that indicate about the Danish bird? (source: Birds of North America (BNA 117, 1994) and http://www.birds.cornell.edu).

Hope you can help with some of the questions.

Thanks in advance

Kent Olsen
Member of the Danish Rarities Records Committee

5 kommentarer:

Kent Olsen sagde ...: Kent,

Regarding the white on the tail feathers, based on information in Pyle (1997) there is no difference by subspecies nor by sex. Every one of the approximately 50-60 Mourning Doves I've banded have had 3-4 tail feathers with white spots. I've never seen any with the 1-3 claimed in the Cornell information. Pyle also notes that differences between the three named subspecies is broadly clinal and gives little to go on as far as distinguishing them visually. No primary projections are given. So, essentially, this is an almost impossible task to assign an out of range Mourning Dove to subspecies. In my experience, the tails of males are longer than those of females. An immature bird would be very easy to discern as they are very distinctly "scaly" on the upperparts. The color differences you describe for the gape would seem very difficult if not impossible to distinguish, especially as there is likely broad overlap in coloration. The bare skin around the eyes is turquoise blue in both sexes.

Allen T. Chartier
amazilia1@comcast.net
Inkster, Michigan, USA; 28. maj 2008 kl. 13.15
Kent Olsen sagde ...: Hi Kent,

Many thanks for your reply: there are two races in the USA and Canada plus a few more in the Caribbean and Central America. To start with the southern subspecies these generally have shorter primaries (as they don't migrate too far) which I guess you could look at if youtrapped it. Most of the southern ones are also darker than the eastern USA birds. In the USA the further west you go the birds get very slightly darker. Although they aren't easy to separate, as your bird looks quite pale then I'd imagine you have an eastern American bird. This would tie in with the fact that at least 2, probably 3 Mourning Doves were seen in the British Isles last autumn (1 in Ireland and 1+ in Scotland). In terms of ageing: the North Uist bird, which I was lucky enough to see, was difficult enough to age with certainty as a first winter. I guess first summers are even more difficult. In autumn (not much use to you!) the primary coverts are white tipped in immature birds but I think they lose this during the winter (and so don't retain a first summer plumage). I think that as the primary coverts are moulted prior to the primaries this feature is lost fairly quickly. In fact some autumn birds might be difficult to age. Having said all that I think there are others who are better informed and more experienced than I.

All the best,
John Bell; 28. maj 2008 kl. 13.33
Kent Olsen sagde ...: Hello Kent,

Thank you for sending the images and congratulations on a great bird. My best guess is that it is an "adult" female of the eastern subspecies carolinensis. But I am actually not 100% sure of either subspecies or sex, since the two interact. The lighting in the images is nice but the low-angle sunlight makes me unsure of how the colors are being reproduced, exactly. Here are some thoughts:

Age: At this time of year the best we can say is that it is not a chick (first calendar year or 1CY). After hatching in the spring or summer (usually), Mourning Doves undergo a complete molt in summer/fall, after which 1CY birds are not separable from older birds by plumage, although they may average a bit duller, sex for sex. A few individuals retain some secondaries in the middle of the tract, and can be aged as 2CY if the retained secondaries are juvenile, or 3+CY if they are adult feathers, but it does not look like your bird has retained any secondaries.

Subspecies/Sex: For an individual in "adult" (definitive) plumage, it looks too dark and brownish on the back to me for the western subspecies marginella, which I see commonly every day here in California. These appear grayer on the back. I also don't think it looks small enough or dark enough for any of the three Neotropical subspecies. In all subspecies, males are bluer on the crown and rosier on the breast than females. The breast color on your bird seems intermediate between the two North American subspecies to me, perhaps because I am used to the duller western subspecies. The crown does not seem to have quite enough bluish for an adult-plumaged male. Thus my guess that it is an adult female. The next most likely possibilities would be a duller male (perhaps 2CY) carolinensis or a male marginella with less bluish on the crown than normal (again, perhaps 2CY). But if the colors are being accurately reproduced in the images, I think adult female carolinensis would make the most sense.

Hope this helps,

Peter Pyle; 28. maj 2008 kl. 20.37
Kent Olsen sagde ...: Andreas Noeske sendte nedenstående links ud på EuroTwitch, WestPalBirds, Surfbirds og EBN idag:

Tour of Europe 2007/2008:
http://www.club300.de/test/dove.jpg

For comments:
http://www.club300.de/id-forum/index.php; 22. juni 2008 kl. 20.05
Kent Olsen sagde ...: Dear Kent,

Thanks for your note. I'm afraid I can't help much on Mourning Dove age or subspecies. I'm sure the age/sex of the bird can be determined. Peter Pyle should be able to give some comments, or he might know who to ask. Since Mourning Dove is a game bird it is very well-studied in the US and there must be someone who really knows these birds from the hunting perspective. I would try to find one of them to comment.

There are trends in color across North America. They tend to be a little darker in the southeast, paler in the west, but there also seems to be lots of variation in each local population so that very pale and dark birds can be found everywhere, just in different proportions. Identifying a vagrant to subspecies would be impossible in my opinion.

Hope this helps,

David Sibley; 12. august 2008 kl. 10.40

Send en kommentar