Horned Lark / Shore Lark 'horns' (1 Viewer)

Nutcracker · Feb 10, 2017

According to Svensson's Identification Guide to European Passerines, moult of Eremophila alpestris is "Adult and young: summer complete". So in autumn, they should be in fresh plumage with their 'horns' at their longest.

Yet in autumn (pic below; mid October), the horns are very short, barely visible, while in spring (when they ought to be at their shortest), they are at their longest and most visible.

What gives? How do their 'horns' get longer in spring? An overlooked partial moult?

Zheljko · Feb 12, 2017

Nutcracker said:
According to Svensson's Identification Guide to European Passerines, moult of Eremophila alpestris is "Adult and young: summer complete". So in autumn, they should be in fresh plumage with their 'horns' at their longest.

Yet in autumn (pic below; mid October), the horns are very short, barely visible, while in spring (when they ought to be at their shortest), they are at their longest and most visible.

What gives? How do their 'horns' get longer in spring? An overlooked partial moult?

Maybe the horns are not counted for the purpose of determining moult types, as they are characteristic for this species only and not for other larks.

Nutcracker · Feb 12, 2017

Zheljko said:
Maybe the horns are not counted for the purpose of determining moult types, as they are characteristic for this species only and not for other larks.

Thanks! Though Svensson gives the moult characteristics individually for each species, not just for each family, so that shouldn't apply.

dantheman · Feb 12, 2017

Presumably it's a hormone related thing - they get hornier in the breeding season.

Nutcracker · Feb 12, 2017

dantheman said:
Presumably it's a hormone related thing - they get hornier in the breeding season.

< groan > 3

AidenD · Feb 12, 2017

I am no expert, but I'd guess that since only the males have the horns, they get longer in the breeding season for courting.

Xenospiza · Feb 12, 2017

Maybe the black feathers get abraded less quickly, thus forming horns?
(based on: https://sora.unm.edu/sites/default/files/journals/condor/v097n02/p0590-p0591.pdf)

Nutcracker · Feb 13, 2017

Xenospiza said:
Maybe the black feathers get abraded less quickly, thus forming horns?
(based on: https://sora.unm.edu/sites/default/files/journals/condor/v097n02/p0590-p0591.pdf)

Good point (pun intended!) thanks! That could well be the answer - and adding to it, the shaft should resist wear better than the vanes, creating a slenderer sharper horn?

Nutcracker · Mar 1, 2017

More details on another thread, thanks to Peter Sunesen

Horned Lark / Shore Lark 'horns' (1 Viewer)

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