Brandon Holden Photography

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A Photo Salon: Variation in the Pine Grosbeak
All pictures taken within the Hamilton Study Area, Ontario, Canada

 

Having several chances to photograph large numbers of Pine Grosbeaks this winter, I have come to notice that there is a lot of variation within the species. Below is a collection of photographs I have taken to display some of this variation. I have broken it down into three parts. 1. Frequently noticed differences in typical birds   2. Frequently noticed differences in un-typical birds  and    3. Strange Individuals.

 

Peter Pyle was kind enough to comment, and allow me to post his e-mail onto this page, about the various birds. His comments appear at the bottom of this page (below all the images). Each image is numbered, to the left, in order to clarify which birds are being discussed.

 

 

1. Frequently Noticed Differences

Most of what I noticed was that 1. Rosy-Pink males actually had a lot of variation in the intensity of the pink, and many had small yellow spots mixed in. Female type birds (both Russet and Yellow birds), showed a lot of variation in the intensity and location of the colour. Possibly age/sex related? See below:

1

A bright male, with rosy-pink colouration in most or all areas.

2

A duller male, with an "off-pink" colour compared to the above bird, and small patches of yellowish feathers (especially in folded primaries)

 

3

A bright "female like" bird with extensive yellowish colouring throughout the body, including the breast.

 

4

A russet bird, showing fairly strong, but also fairly uniform colouration throughout the body.

 

5

A very dull bird, probably a young female, with extensive gray throughout the body.

 

6

A bright male, with a yellow patch near the neck. This was present on only this side of the body. My guess was either a past injury- or feathers lost and re-grown separate from the typical molt.

 

 

2. Frequently Variable

A lot of these birds, I guessed, were young males. A lot of variation in the location and intensity of yellow, orange and red feathers. See Below:

 

7

Mostly russet on the head and rump, with a bit of yellow on the breast.

 

8

Similar to the above bird. Mostly russet on the head, mostly red on the breast, and a mixture on the rump.

 

9

A strange bird, with a general blend of colours over a large area.

 

10

Another blend, but more of a red and yellow mix that is pretty well defined. Little or no colour on the breast.

 

 

  3. Strange Individuals

These were the birds that really stood out of the crowd. Explanations for each below the image:

 

11

This bird was "glowing" compared to the others. I feel this picture does a pretty good job of showing this "neon" plumaged bird, quite unlike any others in the flock, or at all this winter.

 

12

One of the strangest birds I saw, with yellow on the breast and primaries, mostly bright red on the head and rump, and a mostly gray back. This was the only individual I have seen plumaged like this so far this winter.

 

13

Another standout bird. Mostly red on the head and rump seemed strange. The biggest difference however, was that this bird was an entirely different shade of gray (being darker than all of the other Pine Grosbeaks I had seen). The general lack of colour on the breast and back made it even more noticeable. Could a different subspecies be involved here?

 

 

Comments from Peter Pyle:

Thank you for putting this together. It nicely illustrates how it is best to determine age by independent factors, and then use plumage coloration to determine sex. It also illustrates how timing of molt or adventitious feather replacement may affect plumage color. Here are my assessments based on ageing by primary coverts-greater covert contrast, and (where possible) rectrices, then sexing by body plumage:

Birds 1, 2, and 6 are adult males. The yellowish feathering on birds 2 and 6 probably reflect molt-diet and/or molt-timing-hormone interactions. Feathers replaced later or earlier than usual during the prebasic molt, or outside of molt, can show female-like coloring, even in older males that have reached a definitive plumage state. Bird 2 looks like it had an earlier than expected molt (note yellowish to primaries, upper back, and breast, plumage that is replaced earlier in molt sequence), perhaps after a failed breeding attempt and before the hormonal directives (however they work) switched over from yellowish to red. Bird 6 looks like it had lost a patch of breast feathers, as you surmise, probably fairly recently, after the hormonal directive for red had switched back to yellow. We know very little about how and when these switchovers occur (generally in birds or within a species) but perhaps sometime in November-January (red to yellow) and July-August (yellow to red) for adult male Pine Grosbeaks.


Birds 3, 4, and 11 look like first-winter birds, probably males by their bright yellowish or red-tinged plumage.

Bird 5 is a first-winter bird and almost certainly a female, as you surmise.

Birds 7,8,10,12, and 13 appear to be adults and I am guessing older adult females. It is well-known that older females can acquire male-like plumage (as estrogen levels decline and stop masking testosterone) but there may be other factors involved with Pine Grosbeaks. Whether the reddish color results from molt-timing or diet-related interactions or simply that adult females of this species more often can show red would make an excellent subject for further study.

Peter Pyle

 

 

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