Wednesday, September 25, 2013

Clues to a bird's past

by Catherine Greenleaf

When a wild bird comes in for rehabilitation, is it possible to glean some clue as to the bird's past? After all, bird patients can't talk, and we are often forced to play Sherlock Holmes when it comes to figuring out how and why they were injured.

There is one clue that can speak volumes about a bird's history. This clue is called a stress bar. When a bird is deprived of food, that lack of proper nutrition shows up in the structure of the feathers. A lack of proper vitamins and nutrients produces a gap, or nearly transparent space, in the barbules of the feathers, and the result is what you see in the photo above.

This is a feather from a juvenile crow. I have placed it against a roll of white paper towels to make the bars more obvious. You can read the stress bars almost like you would read the rings inside a tree. This bird enjoyed a great amount of nutritious food from the moment he hatched from the egg. The base of the feather is a healthy, dark black, with no gaps or streaking. (Feathers develop from their base) Then as several weeks progress, you can start to see stress bars forming.

This suggests several possibilities:  either one or both adult parents went missing or were killed, could no longer feed their hatchlings and the young nestling crow suffered from starvation and extreme emaciation. The other possibility is the little guy was forcibly pushed out of the nest by jealous siblings competing for food, an event that in rehabilitation is referred to as siblicide.

The other possibility, and the most likely, is that this young crow was removed from the nest by a human, and then brought home and kept as a pet. Or the youngster was found on the ground, at the base of a tree where the nest is located, and carried home. Each year, I get several young crows brought to me by families who admit they thought the baby crow was cute and they had decided to keep him and raise him. However, once a crow gets to the juvenile stage and starts landing on people's heads and pecking with their sharp beak and demanding food at all hours of the day and night, I am asked if there is anything I can do to help. I encounter the same scenario with fledgling ravens.

I say this is the most likely scenario because the other situations usually result in death from starvation or predation. Since the crows that do survive are often fed a diet of Cheerios and Ritz crackers, it often takes 6-8 weeks of rehabilitation to reverse a young crow's nutritional deficiencies. What most often happens is the crow molts the defective feathers and grows in a whole new set, which can take at least 4-6 weeks. What this means is the crow will be with me in rehabilitation for a total of 12-14 weeks on average before being released back into the wild.

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