A Juvenile Double-crested Cormorant at Point Isabel


Claude Lyneis
 

This is the first time I saw a juvenile Double-crested Ccrmorant and initially wondered about the spotted white breast.  It also seemed small, but it was just a young bird.  At the west end of Stege Marsh on the edge of the Marina Bay development.



Alvaro Jaramillo
 

Claude

    This is a great photo to learn from. Usually the term juvenile (juvenal) is restricted to the very first feathered plumage of a young bird. Juvenile Double-crested Cormorants are brown, paler below. Over time they molt their feathers and replace the brown with black. This is what you are seeing, the spotted nature is the replacement of brown with black. But this happens over time, and this bird is not a bird from this year as they have not nested yet. Given the timing and the fact that this is not a brown bird means it is older than juvenile, but not quite an adult. So it is “immature” but not juvenile.

   The other point to consider is that once birds fledge and fly off from the nest, they are essentially at adult size/weight. Sometimes more even! So bird size is not correlated to age, once the bird leaves the nest. There is a lot of size variation in cormorants, I am a bit confused as to why, but some look very small compared to others.

   Thanks for posting this photo.

 

Alvaro Jaramillo

alvaro@...

www.alvarosadventures.com

 

From: EBB-Sightings@groups.io <EBB-Sightings@groups.io> On Behalf Of Claude Lyneis
Sent: Thursday, April 15, 2021 6:13 PM
To: East Bay Birds <EBB-Sightings@groups.io>
Subject: [EBB-Sightings] A Juvenile Double-crested Cormorant at Point Isabel

 

This is the first time I saw a juvenile Double-crested Ccrmorant and initially wondered about the spotted white breast.  It also seemed small, but it was just a young bird.  At the west end of Stege Marsh on the edge of the Marina Bay development.

 

 


Jaan Lepson
 

As a follow-up to Alvaro’s post, my old professor liked to say that birds are the only animals, other than humans,  in which parents take care of fully-dependent offspring as big - or bigger! - than themselves :D

On Apr 15, 2021, at 19:49, Alvaro Jaramillo <chucao@...> wrote:

Claude
    This is a great photo to learn from. Usually the term juvenile (juvenal) is restricted to the very first feathered plumage of a young bird. Juvenile Double-crested Cormorants are brown, paler below. Over time they molt their feathers and replace the brown with black. This is what you are seeing, the spotted nature is the replacement of brown with black. But this happens over time, and this bird is not a bird from this year as they have not nested yet. Given the timing and the fact that this is not a brown bird means it is older than juvenile, but not quite an adult. So it is “immature” but not juvenile. 
   The other point to consider is that once birds fledge and fly off from the nest, they are essentially at adult size/weight. Sometimes more even! So bird size is not correlated to age, once the bird leaves the nest. There is a lot of size variation in cormorants, I am a bit confused as to why, but some look very small compared to others. 
   Thanks for posting this photo. 
 
 
From: EBB-Sightings@groups.io <EBB-Sightings@groups.io> On Behalf Of Claude Lyneis
Sent: Thursday, April 15, 2021 6:13 PM
To: East Bay Birds <EBB-Sightings@groups.io>
Subject: [EBB-Sightings] A Juvenile Double-crested Cormorant at Point Isabel
 
This is the first time I saw a juvenile Double-crested Ccrmorant and initially wondered about the spotted white breast.  It also seemed small, but it was just a young bird.  At the west end of Stege Marsh on the edge of the Marina Bay development.
 
 



=============================
Jaan Lepson

University of California
Space Sciences Laboratory
7 Gauss Way
Berkeley, CA 94720-7451