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

Point Blue Conservation Science: Monthly Banding Summary, September 2019

This summary was compiled by Point Blue’s Palomarin banding interns Samantha Chavez and Hannah Roodenrijs with help from Hilary Allen, Banding Supervisor.

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:

Fall migration is in full swing here at Palomarin! September produced many first-of-fall captures and highlights, as well as the departure of most neotropical migrants for their tropical wintering grounds. Several winter residents arrived throughout the month, and these species will make up the bulk of our captures over the next few months.

The first Fox Sparrow capture of the fall. Photo by Hannah Roodenrijs


The first winter bird arrival was a Hermit Thrush on September 9th. These secretive thrushes are similar to Swainson’s Thrushes but have a rustier-colored upper-tail and can be heard with a small “chup” call. While some Hermit Thrushes do breed in the coniferous forests of Marin County, our wintering Hermit Thrushes are returning from breeding grounds farther north in British Columbia and Washington. Next up we caught a Fox Sparrow on September 12th. These chunky sparrows have distinct chevron markings on their chest and a thick bi-colored bill (a dark upper mandible and a yellow bottom mandible). Their long claws are built for kicking around in the dirt to dig up tasty seeds and insects. This foraging strategy also causes their bands to become very dirty and worn quickly, so we often have to change bands on recaptured Fox Sparrows because the numbers become illegible.

The first Golden-crowned Sparrow of the season! A young bird with a strikingly golden crown with very little black bordering. Photo by Samantha Chavez


A much anticipated arrival here at Palomarin was the first Golden-crowned Sparrow of the season on September 14th. We eagerly anticipate their arrival every year and even have a bet amongst staff, interns, and friends on the date, time, and net in which the first Golden-crowned Sparrow will be caught. This year’s arrival came early, and only two people’s bets landed within 24-hours of the actual first capture.

Two Lincoln’s Sparrows were caught at Palomarin in September. Since this bird also winters here, we expect a few more in the coming months.

A young, first of the season Lincoln’s Sparrow. Photo by Hannah Roodenrijs


By the end of the month, trees around Palo were alive with the sounds of tiny typewriters (that is, Ruby-crowned Kinglets! their chattering call is often described as the sound of a tiny typewriter). We caught our first Ruby-crowned Kinglets on September 24th. Males and females can be reliably sexed based on the presence or absence of a ruby crown. Here at Palo we tend to catch far more females than male Ruby-crowned Kinglets. This is especially interesting because they are one of the only birds that we can determine the sex of here during the winter months.  Though we aren’t certain why that is, we explore some possibilities in a Point Blue study can be found here. Since Ruby-crowned Kinglets are one of the few species that we can sex during the winter, we are unable to determine if a similar sex ratio bias is present in other species that winter here without genetic testing.

Not everyone will be sticking around for the holidays. September had dwindling numbers of Wilson’s Warblers. These cheery yellow warblers are taking their distinctive black caps down to Central America. The Swainson’s Thrushes were also getting ready to make room for the incoming Hermit Thrushes. Many of the Swainson’s Thrushes caught in September were plush with large pads of fat not seen earlier in the season. These birds are stocking up on fuel for their long flight down to Mexico where they will overwinter.

Some birds never reside for a full season at Palomarin but instead pass through on their migrations. If we are lucky, we catch them as they make their way between breeding and non-breeding grounds. Some species such as Western Tanagers, Hermit Warblers, and Yellow Warblers breed elsewhere in Marin, albeit in relatively low numbers, but are usually only captured here at Palo during their fall migration.

A beautiful adult male Yellow Warbler. Only the adult males have substantial red streaking on their breast. Photo by Hilary Allen


Hammond’s Flycatcher. Photo by Hannah Roodenrijs
Least Flycatcher. Photo by Hilary Allen

Some less common fall catches included a Hammond’s Flycatcher and a Least Flycatcher. The Least Flycatcher was especially strange since this bird tends to stick to the eastern United States. We refer to these species that are far outside their normal range as “vagrants”. Aside from having more grey coloration in their head and back, these unusual  flycatcher captures look strikingly similar to our far more commonly captured Pacific-slope Flycatcher. In addition to slight differences in appearance, we also took several detailed measurements to help us identify them to species. These measurements include bill length and width, tail length, projection of the primary feathers, and even the difference in length between specific flight feathers.

And finally, we had another unexpected and exciting capture – a young female Cooper’s Hawk! While it isn’t uncommon for robin-sized Sharp-shinned Hawks to be caught in our nets, it was far more surprising to see the substantially larger Cooper’s Hawk. Extracted carefully and put into the appropriate grip, the hawk was sexed, aged, and some wing and tail measurements were taken before she was released. Like most raptor species, the female Cooper’s Hawks are noticeably bigger than their male counterparts and we can use wing measurements to help us distinguish males from females.

A female Cooper’s Hawk in juvenile plumage. One of the largest birds we will catch in our nets. Photo by Hannah Roodenrijs


We’re looking forward to what exciting captures the fall migration season brings us in the next couple months!

Let’s Do the Numbers:

In 23 days (2686.14 net hours) of mist-netting at Palomarin in September, we captured 236 new birds and recaptured 80 previously banded birds. A total of 316 birds of 34 species were caught. Approximately 14 birds were caught per banding day.

The highest capture rates at Palomarin were on September 24th and September 27th with 20 birds each.

At Palomarin, the following species were caught in the highest numbers: Pacific-Slope Flycatcher (63), Townsend’s Warbler (31), Swainson’s Thrush (26), Song Sparrow (23), Fox Sparrow (21), and Chestnut-backed Chickadee and Brown Creeper (15 each).

No banding occurred at any of the Palomarin off-sites this month. Banding will begin to resume at our off-sites starting this winter.

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.