Tiraya
San Diego CA
Once I was asked why the Mountain Chickadee had a white eyebrow, but the other Chickadee species didn't. All I could suggest was that it reflected light in some way.
Many grass-living species feature these too (as well as supercilia), as do many females of the more colourful species of birds, so what is the true purpose of these marks in different birds? Camouflage?
But of course in the case of Black Ducks and larger birds, is it still camouflage or something different? And this would not explain why many smaller birds that do not lurk in grasses would have them (such as the Mt. Chickadee). Eyebrows appear to be only found in a few species; most if not all related species in the genus or even family do not have it, which is the case in the Mt. Chickadee, White-browed Robin and White-browed Treecreeper. However supercilia are shared with Willow Warblers, Chiffchaffs, Wood Warblers, Sedge Warbler etc. all featuring this trait.
A combination of a dark supercilia and a pale eyebrow seem to affliate with tree-top dwellers, i.e. Firecrest, Pallas' Warbler and Chiffchaff as well as a few marsh species such as Marsh Wren and Reed Warbler(the latter showing ancestry to Chiffchaff/WWarbler?; the supercilia is certainly very pale and inconspicuous on the Reed when compared).
The brighter the eyebrow, the higher in the tree it forages(?) and/or the darker the environment it lives in seems to be relevant, though I cannot really support this.
So there are two types in question:
Eyebrow (lores?) (lighter than head colour) -> Found on birds such as Canada Warbler, Mt. Chickadee, Whinchat, White-browed Robin, White-browed Treecreeper
Supercilium (darker than base head colour)-> Sedge Warbler, Chiffchaff, Little Grassbird, Zitting Cisticola etc.
What seperates Eyebrows and Supercilia, and what are they for?
Discuss.
Many grass-living species feature these too (as well as supercilia), as do many females of the more colourful species of birds, so what is the true purpose of these marks in different birds? Camouflage?
But of course in the case of Black Ducks and larger birds, is it still camouflage or something different? And this would not explain why many smaller birds that do not lurk in grasses would have them (such as the Mt. Chickadee). Eyebrows appear to be only found in a few species; most if not all related species in the genus or even family do not have it, which is the case in the Mt. Chickadee, White-browed Robin and White-browed Treecreeper. However supercilia are shared with Willow Warblers, Chiffchaffs, Wood Warblers, Sedge Warbler etc. all featuring this trait.
A combination of a dark supercilia and a pale eyebrow seem to affliate with tree-top dwellers, i.e. Firecrest, Pallas' Warbler and Chiffchaff as well as a few marsh species such as Marsh Wren and Reed Warbler(the latter showing ancestry to Chiffchaff/WWarbler?; the supercilia is certainly very pale and inconspicuous on the Reed when compared).
The brighter the eyebrow, the higher in the tree it forages(?) and/or the darker the environment it lives in seems to be relevant, though I cannot really support this.
So there are two types in question:
Eyebrow (lores?) (lighter than head colour) -> Found on birds such as Canada Warbler, Mt. Chickadee, Whinchat, White-browed Robin, White-browed Treecreeper
Supercilium (darker than base head colour)-> Sedge Warbler, Chiffchaff, Little Grassbird, Zitting Cisticola etc.
What seperates Eyebrows and Supercilia, and what are they for?
Discuss.
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