|Common Murres at nesting sites|
Their nests are burrows in the ground that usually consist of a long tunnel with a turn right before the actual nest. Cassin’s Auklets will also nest in crevices in rocky habitat. We want to be able to collect data on these birds that breed on the Farallons as a way to monitor the health of the population. Parameters such as reproductive success, timing of breeding, and chick growth and development can be used to accomplish this, and this data can easily be collected by simulating the nest environment using nest boxes. We make the nest boxes out of plywood and construct a tunnel using PVC pipe. The top of the box has a removable lid that allows us to see inside the nest and collect the data.
We are able to look at both mates of a nest because Cassin’s Auklets take turns incubating the egg each day. In most cases, if you find a bird in a box one day, the next day you should find its mate. Checking a nest box is an interesting task. First you must completely block the entrance to the tunnel using your foot or knee so that the bird can’t escape. At the same time you must be able to bend over and peer under the box lid. It’s a bit like doing yoga. If a bird is present, you need to grab it in one swift movement to avoid hurting the egg or the bird. A biologist here described this as being not unlike an alien abduction. Imagine a bright light as the roof of your home opens up, you are snatched up, measurements are taken and you’re returned with a metal band on your ankle. I try to keep this perspective in mind when I’m holding a Cassin's and its beak is clamped down on my fingers or its claws have lodged themselves under my cuticle. I also know that the collection of this data will aid in monitoring these birds.
We can track specific individuals in a population by putting a metal band around their leg with a unique number for each bird. We know the ages of birds that we banded as chicks, and we always check band numbers to see if a bird we find is one of known age. We also band birds that are mates of known age birds.
When known age individuals are found, both they and their mates have condition data recorded. This includes measuring the bill depth (used to sex the individual), wing cord length, weight, and egg size.
|Measuring the length of an egg|
|Measuring the wing cord of a Cassin's Auklet|
|Bird in a bag|