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is this cormorant moulting ? (1 Viewer)

marnixR

WYSIWYG
is my assumption that the cormorant in the attached picture is moultng its head feathers, or is something else going on ?

picture taken earlier today on the river Taff near Radyr Weir on the outskirts of Cardiff
 

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The white feathers ('filoplumes') are used for pre-breeding display, so now's the time of year they appear :t:

In general, the older the bird, the more white feathering it has on its head (a bit like people there!!), it's a sign of dominance / breeding quality.
 
funny that, i’d never noticed this feature on cormorants before
do the filoplumes disappear or get hidden later in the year ?
 
here's the same cormorant (i assume) eleven days later - seems like he's gone in for a badger lookalike competition :-O
 

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i just placed the 2 pictures next to one another, and i must say i have trouble seeing a significant difference - could it be the result of poorer light in the second picture ?
 

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i just placed the 2 pictures next to one another, and i must say i have trouble seeing a significant difference - could it be the result of poorer light in the second picture ?
Nope, they're really different. Even if you can't see it, you can measure it.
The angle is slightly different between both photos, but it's not significant imo.
There are many possible ways to verify this. For example, if you measure the distance going from the rear end of the eye to where bill meets frontal feathering (A) and then you compare this to the distance from frontal feathering to bill tip (B), you get (B/A): 2.21 for the long billed (and bulbous tip individual; the bird on the left hand side the composite image) and 1.77 for the shorter billed (and finer tipped; the bird on the right hand side) individual. There are other structural, perhaps more subtle, differences.
 
I’ll take your word for it

I just find it strange that on both dates there’s a bunch of “normal” cormorants with only one with the filoplumes - or is that to be expected ?
 
I’ll take your word for it

I just find it strange that on both dates there’s a bunch of “normal” cormorants with only one with the filoplumes - or is that to be expected ?

I can't answer to that exact question. What I can say is that all Cormorants (with no exception afaik) that are going to breed this year will develop (if they haven't yet) filoplumes. Those birds are likely to get closer to their breeding grounds as breeding season approaches. The filoplumes are used mainly during the short display period, at the beginning of the season, being gradually shed as they start incubating the eggs. This is the normal plumage for breeding adults during this period. The ones with no filoplumes are either immatures or eventually non-breeding adults. Filoplumes are present in many (most) cormorant species throughout the world (and are equally exhibited during a short period). So nothing odd here.
I'd put your question differently: how probable would it be that 11 days since the first observation you'd see exactly the same individual of such a common and mobile species in the same spot? I'd expect adults to be moving a lot right now. You'll be seeing more birds like this as you start paying more attention to this plumage now, I'm sure.
 
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