Everything you wanted to know about bird anatomy but were afraid to ask - Dec 20th

You must know by now that until 3 weeks ago I knew very little about birds. In case you are in the same boat as me, here is a crash course in the really cool things about birds that you didn’t know that you didn’t know:

During the breeding season female birds have a brood patch. Feathers are a great insulator and will trap air around a bird to keep it warm. But during the breeding season, the female needs to keep eggs warm as well as herself. So she develops a patch on her abdomen where she can put her warm skin into contact with the eggs and keep them at the right temperature.

At the base of the tail, birds have what looks like a huge pus-filled pimple. When you squeeze it, a pus-coloured liquid actually does come out of it. This is the preen gland and the substance which comes out is the preen wax. Birds use this to preen their feathers and make them waterproof.

Talking of feathers, baby songbirds hatch out of the egg without feathers. Melanie tells me that songbirds have ‘altricial’ chicks, rather than ‘precocial’ chicks. While precocial chicks hatch with feathers and are ready to follow their parents a few hours after hatching, such as ducklings, altricial nestlings are naked, have closed eyes for several days and their skin looks like the skin you see on a supermarket chicken. The skin is so thin that I think that I could see their organs if I looked closely enough. After a few days, the nestlings get covered with rows of short pins, which look a bit like candles. The top parts of the pins break open (in black robins when they are around 9 to 10 days old) and eventually the new feather emerges from the pin. This stage is called “pin break”.

We look out for when nestlings are at pin-break stage, because this is the time when we film the nests. After that the nestlings start looking more like miniature versions of their parents rather than characters auditioning for the Muppet Show!

Baby birds have huge beaks and the inside of their mouths are brightly coloured. This colouration makes it obvious to the parents where they should put the food.

The birds’ beaks also seem to be at adult size from a very young age, but despite these huge mouths, bulging eyes, big bellies and a general air of ugly helplessness the nestlings really are terribly appealing.