Everyone knows a bird when they see one, but birds have some interesting features that make them unique in the animal kingdom.
One thing common to all birds is that they have feathers.
We think of birds as being able to fly, but there are birds that don't fly.
Think penguins and Emus.
A bird's feathers are analogous to skin in most other animals.
Like skin cells, the feathers sustain a great deal of wear, and don't last a bird's lifetime.
The growth of feathers and replacement as they wear is called molt in birds.
Molt is a well-known but not completely understood phenomenon in birds.
Some birds are born naked or nearly naked of feathers, and are called altrical.
Others are born with a full set of downy feathers and leave the nest almost immediately and are called precocial.
Most birds have a complete molt of feathers once a year, called the basic molt.
This usually happens after breeding in adult birds.
First cycle birds grow their juvenile feathers after hatching.
Some species keep these juvenile feathers until the next year at the first full basic molt.
Others replace some or all of the juvenile feathers in a special molt later in the first year called a preformative molt into the formative plumage.
Birds who have a formative plumage in the first year are said to have a complex strategy of molt.
Some birds are commonly known to have a different plumage in the breeding season than in the non-breeding season.
These may change by wear of their basic plumage feathers to a different appearance, as in many blackbirds, or by a pre-alternate molt into an alternate plumage that typically occurs prior to breeding season.
There remains much to understand about feather molt in many species, but in the last 10-15 years much study has led to a better understanding of avian molt.
One thing common to all birds is that they have feathers.
We think of birds as being able to fly, but there are birds that don't fly.
Think penguins and Emus.
A bird's feathers are analogous to skin in most other animals.
Like skin cells, the feathers sustain a great deal of wear, and don't last a bird's lifetime.
The growth of feathers and replacement as they wear is called molt in birds.
Molt is a well-known but not completely understood phenomenon in birds.
Some birds are born naked or nearly naked of feathers, and are called altrical.
Others are born with a full set of downy feathers and leave the nest almost immediately and are called precocial.
Most birds have a complete molt of feathers once a year, called the basic molt.
This usually happens after breeding in adult birds.
First cycle birds grow their juvenile feathers after hatching.
Some species keep these juvenile feathers until the next year at the first full basic molt.
Others replace some or all of the juvenile feathers in a special molt later in the first year called a preformative molt into the formative plumage.
Birds who have a formative plumage in the first year are said to have a complex strategy of molt.
Some birds are commonly known to have a different plumage in the breeding season than in the non-breeding season.
These may change by wear of their basic plumage feathers to a different appearance, as in many blackbirds, or by a pre-alternate molt into an alternate plumage that typically occurs prior to breeding season.
There remains much to understand about feather molt in many species, but in the last 10-15 years much study has led to a better understanding of avian molt.
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