Wednesday, March 17, 2010

Boneyard

A small 3-stall boathouse at the Marshland Unit of Sea Rim State Park has served as a nesting site for cliff swallows since 1989. During the spring and summer months I would often stop by to watch literal clouds of these and three other swallow species- barn, cave, and tree feed over the nearby fields. Unfortunately all that remains of the this spot, following Hurricane Ike, is a mere skeleton of the previous structure. As I walked around the remnants of a neighboring attached structure I spotted an owl pellet on the ground. Owls along with other birds (hawks, shrikes, herons, swallows, jays, flycatchers, etc.) cough up oblong shaped capsules containing parts of the animals they eat that their bodies can’t digest, mostly fur, bones and feathers.

I came to the assumption that the pellets belonged to an owl, due to their size and contents, and also because of the presence of whitewash (owl feces) indicating they’ve been roosting here. Hawks usually tear their prey into bite size pieces as they eat resulting in a pellet that may not contain large identifiable parts.


Owls on the other hand swallow their prey whole resulting in a pellet containing the complete skeleton and fur of its meal. I also came across another site nearby where a number of pellets over time had broken down leaving behind a small “boneyard” consisting of jaw, leg, skull and other bones.

This area was more exposed to the elements allowing the pellets to get wet which in turn dissolved the mucus that held them together. Fur was then washed away leaving behind a swell of bones.

Miles of open savannah surrounding this marshland coastal ecosystem provide perfect habitat for mice and voles. I think that owls hunting these fields at night are using this structure to feed and in turn, expelling pellets from prior meals on the ground below their perches. Where are these owls roosting during the day I wondered? I came to the conclusion that the closest place would be Sabine Woods which is about 3 miles down the road from here where I’ve seen both barn and great-horned owls. I’m considering setting up a camera trap at this location, which may provide some interesting photographs and prove if owls are responsible for this “boneyard”.

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