By the numbers

Post date: Jun 2, 2013 6:29:31 PM

Conservation biology is a numbers game. On an individual level we use numbers to compare total populations of species, present and past, and determine how quickly they die or reproduce. On a broader scale, we use numbers to measure habitat, to see whether it is growing or shrinking, and to decide which pieces of land to protect. Although the statistical and modeling tools we use are complex, they run on a steady diet numbers, which can only be supplied by going out and, well, counting things.

Our work in Texas coincided with waterbird censuses on both of our island capture sites, and we were lucky enough to help out. Ordinarily, we try to keep away from the rest of the colony while doing our work. Many waterbirds nest in trees, which keeps them safe from most predators but puts their awkward, flightless nestlings at risk of falling if they're disturbed. Censuses are our only chance to peer into the secret lives of herons, egrets, ibises, and spoonbills, before we leave them to finish nesting in peace.

Great Blue Heron nestling (Chester Island)

Tricolored Heron chick (Chester Island)

White Ibis nestlings (Chester Island)

Our first census was on Shamrock Island. With nine people and two boats, we were able to divide responsibilities so that some counters worked from the interior of the island while others remained on the water to count birds as they flushed from their nests.

Elizabeth and USFWS assistant Frank getting ready to count

Artist's rendering of the island and some of its birds (not to scale...)

Unusual blue Laughing Gull eggs

Nesting Caspian Terns and Laughing Gulls

No final tally yet, but usual numbers from the island are around 20,000 total pairs of nesting birds.

A few days later, we headed out to Chester Island in Matagorda Bay. Like the count on Shamrock, we had a large team and were able to split up to count separate areas of the island. Two groups focused on the open areas at the north and south ends of the island, packed with nesting pelicans and terns, while the third group stayed in the tall vegetation near the center of the island to count the more secretive tree-nesters.

How many species?

Counting in the sunflower jungle

Roseate Spoonbill chicks

And pelicans, of course

In a morning's work, we counted over 13,000 pairs of birds, including over 3,300 pairs of pelicans. Elizabeth also saw our team's first rattlesnake of the summer. All in all, it was great to take a break from the pelicans and contribute to ongoing monitoring of these critically important colonies.