My life is about living with nature – here you can live it with me!

Bird “Parts”

I am soo going to regret posting this because I am just going to get all kinds of sp@m from the verbiage that I am using! Today I visited Sharon’s “California Hill” MAPS banding station which is located about 45 minutes north of my house. Sharon has been helping me band birds at my stations for just about as long as I have been banding birds. It is nice that on my off days that I am able to assist her with her banding station. Today I was able to capture a few great bird photos but I will be posting them at a different time (maybe a birdQUIZ??)! I want to focus on today’s post with something unusual that we found on one of the birds. Before I get into that find, lets first talk about a few of the bird parts that us banders need to look at while banding!

blowing away the feathers

You will always find us bird banders quickly blowing the birds feathers around and looking at many things under its feathers. What we find can assist us in determining its gender it is and how much fat the bird is storing. During our MAPS banding (breeding season) we rarely find any fat built up due to most of the bird’s energy is being used in incubating eggs, feeding nestlings or protecting a territory. When a bird does store up fat, they typically are doing so for energy during migration or for surviving a cold night. What we are looking for (we can see through the skin) is the yellow fat that we pull off our raw chicken meat. (I see it all the time; I buy the cheap boneless chicken.)


Cloacal Protuberance of a male Song Sparrow

During the breeding season, most of the male birds have what is called a Cloacal Protuberance (CP) which is used for storing sperm and assist with copulation. These CP’s start developing in early spring and reach their peak size close to the timing which eggs are to be laid by the females. By late summer the protuberance by the males will slowly recede is size (to no protuberance) until the following spring when the cycle happens all over again. It is almost like going through puberty once a year for as long as they live (ugg)! During the breeding season we use this CP for identifying males in species that have similar plumages but some females can develop a very small protuberance (so we need to be careful with a small chubbies). BTW: at our banding station, we call CP’s “chubbies” since we have many kids around!! (Example, no chubby, small chubby, medium sized chubby and large chubby (big boy).)

Looking at a Brood Patch

An Indigo Bunting Brood Patch

Some species of birds will develop what is called a Brood Patch (BP) which is used for transferring their body heat to the eggs during the incubation period. The parents will loose the feathers around their belly and the blood vessels around the bare parts will then begin to swell (which will then keep the eggs warm). Typically you will find these BP’s in female birds but there are many male species that assist in incubation of the eggs and will also develop a BP. Many of our brood parasites birds like the Brown-headed Cowbirds will never receive BP’s because they never incubate eggs.


Female Gray Catbird with a Growth

As I previously mentioned, today we found something unusual. Sharon blew the feathers away from this Gray Catbird and quickly noticed something much larger than your typical chubby. We knew this was a female Catbird due to its obvious BP but something else was going on here. Does this bird have a tumor?? It is obviously MUCH larger than any other chubby we have ever seen before!! On only a few other occasions have we located a growth around its Cloacal area but we do find other defective areas in a very tiny percentage of birds that we have captured. So what is going on here?

growth and brood patch

Female Gray Catbird with a Growth and Brood Patch exposed

Sharon and myself both agree that this is probably some kind of tumor or growth on this bird. Is this causing some hormone problems with this bird?? It is very possible but I am not a doctor and only speculating what is wrong with it! With bird banding we are keeping different measurements of the birds (including its growth) and we then can keep track of any changes with this bird if it is ever captured again. Do note that this bird was very health; its weight was right on with other female Catbirds and it appears to have successfully laid eggs since it does have a Brood Patch. Although, I do think this bird might be a little sad since I have flashed her photos of her under parts across the internet!! I sure hope Sharon is able to capture it again here in the near future!!

12 responses

  1. Ineta

    Great information! Awesome captures!

    24 June 2007 at 1:14 am

  2. There are just too many possibilties for wisecracks here-I’ll leave those for someone else and just say-thanks for the educational post!

    24 June 2007 at 5:36 am

  3. Well now… Cloacal Protuberance… news to me. I assumed immediately that I was looking at a brood patch on those first photos. Maybe unless someone is looking for bird porn you’ll be safe from the spam Monarch! Thanks for sharing some really interesting information.

    24 June 2007 at 8:05 am

  4. @ Ineta, thanks and glad you came over to my blog from flickr!
    @ Larry – Thanks and I can think of many here also! I wanted to do something a little different on here than my normal reports. Next banding is on Monday!
    @ Jayne – those first two photos were taken of a “big boy” Song Sparrow that doesn’t really show its size as big as it really was! Ugg, already up to 8 sp @ m’s that have been focused on s(e) x already! Ugg!

    24 June 2007 at 8:36 am

  5. Thanks for the education on birding underbellies and things Tom! I feel bad for the birdie with the tumor. Thankfully wordpress has a great spam filter, huh!

    24 June 2007 at 8:44 am

  6. Now I really have learned something new today. Your site is always so interesting and informative. Thanks for taking one for the team.

    24 June 2007 at 2:23 pm

  7. Marg

    Poor Catbird, how embarassing for her, when she’s famous you’ll be posting these shots all over the web (oh wait you already have ;D)
    I do feel sorry for her on a more serious side a Catbird was singing away when I was in the Park this morning

    24 June 2007 at 3:32 pm

  8. @ Pam – thanks and I feel bad also! They do have a great filter!
    @ Trixie! Soo glad you were able to learn something! It does get hard to post new things on here!
    @ Marg – I feel bad for the catbird also! LOL

    24 June 2007 at 9:01 pm

  9. Haha.. seems you too have a fascination with bird nether regions. Sorry, but your big boy Song Sparrow doesnt hold a candle to this Oxyura:

    25 June 2007 at 9:31 pm

  10. You know, I was aware of all the bird’s “naughty bits” as Birdchick calls them, but photo evidence of said bits….thanks, Tom.
    And going through puberty every year…yikes. No wonder male birds act so squirrelly.
    I hope I don’t get nightmares of chubbies…..

    25 June 2007 at 11:03 pm

  11. @ Nick, looks like that duck has more problems than any other that I have ever seen!
    @ Susan – it has been a while since I have been over to Birdchicks site! I see see what she has been posting lately! BTW: Did you have any?? They are very harmless!

    26 June 2007 at 10:00 am

  12. Kat Kitts

    Thanks for the explanation. I attended a bird banding Saturday and heard the terms CP and brood patch, but didn’t know what they were.

    23 April 2012 at 11:18 am

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