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Point Blue Conservation Science: Monthly Banding Summary, May 2019

This summary was compiled by Point Blue’s Palomarin banding interns Sarah Mueller and Olivia Wang with help from Hilary Allen, Banding Supervisor, and Diana Humple, Palomarin Program Lead.

About Point Blue: Our mission is to conserve birds, other wildlife, and ecosystems through science, partnerships, and outreach.

Our Vision: Because of the collaborative climate-smart conservation work we do today, healthy ecosystems will continue to sustain thriving wildlife and human communities well into the future.

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Exciting Captures and Observations:

May is a busy time for the Palomarin interns with the breeding season in full swing. Marin county’s resident species as well as the species that migrate here to breed are all nesting now, and almost all the adult birds we captured this month showed breeding condition (see our April monthly banding summary for more information on “breeding condition”). Throughout the month we saw signs of breeding including birds carrying nesting material or food for nestlings, and we even found a few nests around Palomarin and our off-sites.

Some nestlings are beginning to fledge, and toward the end of May, we captured our first juvenile songbirds! The very first juvenile songbird captured by the summer interns was a Chestnut-backed Chickadee on May 22nd at Palomarin. Juvenile birds are generally the same size as their parents but often have different plumage. Within the first week or two after leaving the nest, they will also have a brightly-colored fleshy gape at the corners of their bill. Another useful technique the banders use to determine the age of birds is skulling. When juveniles first leave the nest, their skulls have only one layer of bone. Throughout their first summer and into fall, they grow a second layer of bone in a process called ossification, and banders can use the pattern of the skull ossification, which they can look at through the skin on the bird’s head, to determine whether a bird is a juvenile.

A juvenile Chestnut-backed Chickadee. A yellow gape is visible at the base of the bill, and the head is sooty gray rather than light brown in color. Photo by Olivia Wang


A juvenile Pacific Wren. A yellow gape is visible at the base of the bill. Photo by Olivia Wang


We had some exciting first-of-season and unusual captures in May. The banders captured our first Black-headed Grosbeaks—a common breeding season migrant in Marin—on May 14th at Redwood Creek in the Golden Gate National Recreation Area. Also on May 14th at Redwood Creek, we captured an adult male Hooded Warbler – a vagrant warbler from the eastern US! At Palomarin on May 18th, we captured a Brewer’s Sparrow, common in sagebrush habitats in eastern California but only the third ever captured at Palomarin. Other exciting captures included Cedar Waxwings (May 2nd, Pine Gulch in the Bolinas Open Space Preserve), a Northern Flicker (May 9th, Muddy Hollow in Point Reyes National Seashore), an Olive-sided Flycatcher (May 25th, Palomarin), and a Savannah Sparrow (May 28th, Pine Gulch).

Adult male Hooded Warbler. Photo by Sam Snowden


Adult Cedar Waxwing. Red waxy tips are visible at the end of the wings. Photo by Olivia Wang


Adult female Savannah Sparrow. Photo by Sarah Mueller


We had some unusual weather here at the field station this May. Typically we have fair weather in May at Palo, and aside from drizzly or foggy mornings, the days are mostly dry and mild. This year, we had a substantial rain storm in the middle of the month. Over a 24-hour period (from midnight to midnight) on May 18th, we recorded 44.5 mm of rain. This is the second highest record of rain fall in a 24 hour period in May since we started recording precipitation here at the field station in 1975! The only other day (24 hour period) in May with a higher total rainfall was in 1996 with 64.8 mm. In addition to having the second wettest day on record, May of 2019 also was the third wettest month of May that we have had since 1975, with a total of 96.1 mm of rain over the course of the month. The other two years with wetter Mays were 1998 and 1996 with a cumulative monthly May rainfall of 130.6 and 108.4, respectively.

Let’s Do the Numbers:

In 25 days (2916.96 net hours) of mist-netting at Palomarin in May, we captured 116 new birds and recaptured 159 previously banded birds. A total of 275 birds of 26 species were caught. Approximately 11 birds were caught per banding day.

At our other West Marin banding sites, we captured 242 new birds and recaptured 175 previously banded birds. A total of 417 birds of 38 species were caught over 12 banding days in April (741.74 net hours), an average of approximately 35 birds per day.

The highest capture rates at Palomarin ended up being a 4-way tie between May 5th, 7th, 14th, and 20th, all with 16 birds. The highest capture rate at our other West Marin banding sites was May 14th at Redwood Creek with 55 birds!

At Palomarin, the following species were caught in the highest numbers: Wilson’s Warbler (70), Swainson’s Thrush (54), Allen’s Hummingbird (24), Orange-crowned Warbler (18), Pacific Wren (11), and Song Sparrow (11).

Across all off-sites, the highest numbers of captures by species were: Swainson’s Thrush (101), Wilson’s Warbler (73), Song Sparrow (60), Allen’s Hummingbird (36), and Orange-crowned Warbler (26).

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.

Our Palomarin Field Station is open to the public.  Consider visiting us!  Learn how on our contact & visit us web page.