Friday, October 9, 2015

AHY Male Yellow-rumped Warbler

Finding a deceased bird is not the most joyous experience, but it offers an opportunity for detailed study. The following image (Fig. 1) shows the vibrant yellow patch that the Yellow-rumped Warbler is named for. A hint of the yellow in the crown is also visible.

Figure 1. Yellow-rumped Warbler dorsal view. Photo by Alix d'Entremont.

All Yellow-rumped Warblers have mostly brownish upperparts in fall, but AHY (after-hatch-year) males typically show the greatest amount of blue-gray (MBO). Figure 1 shows blue-gray on the coverts, scapulars, mantle, nape, and the rump area. Notice the wide dark centres to the uppertail coverts which is more extensive on older birds and males (Pyle, 1997).

AHY males show on average the greatest amount of yellow on the breast and crown (Fig. 2). AHY males are the only age/sex class in fall to sometimes show traces of black in the lores or auricular (MBO). Black lores are clear in Fig. 3.

Figure 2. Yellow-rumped Warbler underside. Photo by Alix d'Entremont.
Figure 3. Yellow-rumped Warbler head. Photo by Alix d'Entremont.

The wing of AHY males show very little contrast between feather groups - it is dark overall (Fig. 4). A hatch-year bird would show contrast between the greater coverts and the rest of the wing (primaries, primary coverts and secondaries). This contrast in young birds is due to the dull, retained juvenal feathers compared to the newer and darker greater secondary coverts. AHY females have browner and duller wings than those of AHY males. (MBO)

Figure 4. Yellow-rumped Warbler wing view. Photo by Alix d'Entremont.

Figure 5 shows that white is present on on the outer 3 tail feathers (r4-r6) and that the base colour of these is blackish. Pyle (1997) cautions that there is more overlap in rectrix shape by age in Yellow-rumped Warblers than in other Dendroica warblers. Nevertheless, the tail feathers of this bird appear fairly blunt-tipped like an AHY bird.

Figure 5. Yellow-rumped Warbler tail. Photo by Alix d'Entremont.


McGill Bird Observatory (MBO). (n.d.) [Photo Library: Yellow-rumped (Myrtle/Audubon's) Warbler / Paruline à croupion jaune (Dendroica coronata)]. Retrieved October 9, 2015.

Pyle, P., S.N.G. Howell, R.P. Yunick, and D.F. Desante. 1997. Identification guide to North American Birds, Part 1, Columbidae to Ploceidae. Slate Creek Press, Bolinas, California.

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