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Taking the Long View: An inside look at the goings-on at the longest running avian ecology field station west of the Mississippi.

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Palomarin Monthly Banding Summary: May 2021

August 6, 2021

This summary was compiled by Point Blue’s Palomarin banding intern Joelle Carbonell with help from Mark Dettling, Banding Supervisor.

Exciting Captures and Observations:

This month, we celebrated the arrival of migratory Swainson’s Thrushes from Mexico. These migrants return to breed and they begin setting up territories by singing. Their “flutey”, musical songs signal the coming of summer. They have a fun variety of calls with some sounding like water dripping and others like goats bleating. Like other thrushes, they have long legs and large eyes. Their summer diets consist largely of berries which often make an appearance while banding due to their tendency to poop in the hand. For more on how we know where they migrated from, see here!

Some other new arrivals included several hatch year birds! Most of the birds here were in eggs for about two weeks and hatched to then spend two more weeks as nestlings. Once they “fledge” or leave the nest, we may catch them in our nets. We caught our first hatch-year (i.e. their first year of life) Oregon Junco on May 13 and our first hatch-year Orange-crowned Warbler May 19.

Young birds often have a “gape”. You can see it at the corner of this hatch year Orange-crowned Warbler’s mouth. Having a brightly colored mouth acts as a target for the parents to know where they should put food. Photo by Joelle Carbonell.

 

Another exciting catch included a female Brown-Headed Cowbird. Their very interesting breeding strategy is called nest parasitism. Instead of going to all the trouble of making their own nests and feeding their own young, they employ (read: force) other nesting birds’ help. By sneaking their eggs into the nests of other birds, they avoid most of the work involved in raising the next generation. Cowbirds develop more quickly than the host young, giving them an advantage in the nest. However, if that isn’t enough they may also toss eggs or other nestlings out to ensure they receive attention from the parent. Because cowbirds are often larger than the species they parasitize, this can result in a small adult feeding a huge baby. Although it seems like the host parents should recognize this hulking cowbird is not their baby or even the same species, birds have quite the blind spot when it comes to their young (like some humans).

This Brown-Headed Cowbird female was an unusual catch at Palo. Like many species with sexual dimorphism (where the males and females look different) the female is less showy and mostly brown. Photo by Joelle Carbonell.

 

Let’s Do the Numbers:

In 25 days (2,556.5 net hours) of mist-netting at Palomarin in May, we captured 99 new birds and recaptured 130 previously banded birds. A total of 231 birds of 30 species were caught. Approximately 9 birds were caught per banding day.

The highest capture rate at Palomarin was on May 16th with 18 birds.

At Palomarin, the following species were caught in the highest numbers: Swainson’s Thrush (45), Wilson’s Warbler (25), Orange-crowned Warbler (18), Oregon Junco (17), Song Sparrow (16), and Wrentit (14).

Song Sparrows are one of our study species at Palo. Because we are interested in studying them more closely, each bird receives a unique color combination which allows us to identify an individual in the field, without capturing it. This particular bird’s combination is S/REO (silver aluminum band on the left leg, red, emerald, and orange on the right). Photo by Joelle Carbonell.

 

Steller’s Jays are beautiful in the hand! Blue is a unique color in nature because it is structural. Unlike other colors which come from pigmentation, blue is only blue because the feathers scatter the light in such a way that allows us to perceive blue. Photo by Joelle Carbonell.

 

Adult Wilson’s Warbler, one of the migratory breeding species at Palomarin. Photo by Amaya Bechler.

 

About these Summaries:

Point Blue interns and staff at our Palomarin Field Station share these blog posts in an effort to further engage the public in our science. We are grateful to our partners at the Point Reyes National Seashore and to our surrounding Bolinas and West Marin County community for their support of our work.

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