Winter 2023-24 Banding Summary (November through February)

May 20, 2024

This summary was compiled by Point Blue Avian Ecologist and Banding Supervisor Mike Mahoney, with help from Larissa Babicz, Banding Supervisor, Diana Humple, Senior Avian Ecologist and Banding Coordinator, and Mark Dettling, Avian Ecologist.

Exciting Captures and Observations:

With the breeding season in full swing in the scrub outside our doors and many neotropical migratory birds still returning to the coasts of the North-central California, it’s a great time to reflect on the past winter and all that it brought to the Palomarin Field Station (Palo).

This winter, we continued the trend started this fall and brought back a crew of returning apprentices, with their apprenticeships lasting a couple to several months in length. While we do not anticipate continuing to hire only returning apprentices in future fall and winter seasons, it was an awesome opportunity to have banders, who we all enjoyed working with, return to the field station. Not only did they bring excitement and enthusiasm, but they also brought new skills and perspectives from field jobs they had during their time away from Point Blue. In November, we welcomed back Kevin G. and Doris R., after they completed a hawk watching season and cross-country drive from their field site in Minnesota.

November typically marks the unofficial end of landbird fall migration. Across most of the United States, sparrows are some of the last migrants to move south for the winter. At the field station, we were reminded of this phenomenon when we captured a migratory Slate-colored subspecies of Dark-eyed Junco (a species of sparrow) on November 1st. We most often encounter resident (ie. here year-round) and migratory Dark-eyed Juncos of the Oregon subspecies, so this individual was an unusual encounter!

 

This was a HUGE year for a different migratory sparrow: Swamp Sparrow. Between November 1 and February 28, we had 13 Swamp Sparrow captures, making the winter 2023-2024 highest number of captures for for this species in a winter in almost thirty years of banding at Pine Gulch, our banding site at Marin County Parks’ Bolinas Lagoon Preserve, where we most often encounter these unusual wintering birds. Swamp Sparrows breed in boreal forests of eastern and central North American, and while most migrate to the south-central and southeastern United States to spend their winter, a small number of these birds end up spending the coldest part of the year in coastal California.

 

 

November not only marked a change in season; it also marked a change in infrastructure at the field station! Thanks to the support of a truly generous donor, in November, we started the renovation of the bathrooms in the residential building.

Early in the winter, we captured two Pileated Woodpeckers: one hatch-year (ie. hatched this calendar year) female bird on November 22nd and a second-year (ie. hatched last calendar year) female on December 5th. Biologists at the field station have noticed a trend: as the forest around our banding station continues to mature, we are seeing more of these forest dwelling woodpeckers in our nets. Like with the Swamp Sparrows and Pileated Woodpeckers, at the field station, we use trends in captures over time to try and tell stories about how our local bird populations are responding to environmental changes, whether that be because of climate change, human management, etc.

 

Bird banding, when paired with other techniques, can also be a great tool to understand bird movement. While we at the field station are using new technologies to follow birds across their full life cycle, when we put our low-tech aluminum bands on birds, we are unable to tell where an individual may have gone in between the times it was captured in our nets. Birds captured with bands already on their legs are known as recaptures, and we recapture many of our previously banded birds, with different rates of recapture across the year. Because many songbirds show site fidelity (meaning they show a tendency to return to the same location annually), nearly all our recaptures are from birds that we have previously banded at our field station, rather than ones that originated at a different site, known as foreign recaptures. Every day, banders enter capture data into our database and read what we call our “recap-report”, or a summary of the previous captures pulled from our database. However, in early December, banders recaptured a Sharp-shinned Hawk in the Palo nets and were unable to find the bird’s first record in our database.

Because the United States Geological Survey’s (USGS) Bird Banding Laboratory (BBL) prints and issues bird bands and permits to bird banding stations across the United States, no two birds have the same band number. Additionally, the BBL houses bird capture data for all banding operations across the US. Using their online portal, we were able to look this individual up in their database and learn that it was originally banded at the Golden Gate Raptor Observatory (GGRO), a project of the Golden Gate National Parks Conservancy located in the Marin Headlands, on September 28, 2022 as a hatch-year (ie. hatched that calendar year) bird.

 

 

How did this foreign recapture end up in our nets? It’s hard to know! In 2011, Point Blue scientists at the Palomarin Field Station published a scientific article titled, “Patterns in Movement, Captures, and Phenology of Sharp-shinned Hawks in Central Coastal California,” where they investigated our Sharp-shinned Hawk capture data (Check out the publication here: link). They learned that our banding data suggest that Palo is a point on a migratory route and/or a destination for some wintering Sharp-shinned Hawks. The authors also noted instances of birds from Palo being capture at GGRO and vice-versa, and they indicated that more study is needed to determine where these birds are heading!

 

 

In early December we said good-bye to Naomi B. and Wren L., and we welcomed back Larissa B. after her fall on the Farallon Islands! It was predicted to be a wet winter, but forecasted impacts of El Niño did not produce the number of atmospheric rivers experienced during the 2022-23 winter. Regardless, banders still battled wind and wet weather, typical of a winter banding season.

On January 1st we celebrated bird birthdays! One of the most important pieces of data we can collect on our birds, in addition to getting a band on their leg, is the bird’s age. We use things that we can see in the hand like development of the bird’s skull and shape of their feathers, to help us discern younger birds from older birds. Like many stations across temperate North America, we use an aging system that uses the calendar year to categorize birds into cohorts of time-since hatching. That’s why, on January 1st all birds experience a birthday: hatch-years become second-years, and after-hatch-years become after-second-years. It is a joyous occasion usually involving cake and a little bit of head scratching in the days following as banders become accustomed to the change.

In January, in addition to running the nets, banders started to collect additional data on the forests around Palo to help us quantify the amount of fuel (ie. woody material) in our study area to aid in our efforts to understand how habitat change at the site is impacting local ecology.

 

On January 20th at the Palomarin nets, banders captured an overwintering Hermit Warbler! While some individuals are known to spend their winter around the Bay Area, this is the first wintering Hermit Warbler captured in the Palo nets since 2012. We’re not sure what influences these birds to overwinter in our area. This capture could be an effect the area’s mild winter or how the now-forested habitat around our nets is becoming more suitable for Hermit Warblers.

Hope C. returned to the Palo just in time to experience the storm of the winter on January 31. The hurricane force winds associated with the storm toppled many Eucalyptus trees on Mesa Road, knocked out power to the field station and much of Bolinas (and wider west Marin), and put Bolinas under a temporary shelter-in-place due to the number of power lines downed by the storm!

February was a rainy month with lower capture rates, but the Palo banders still found ways to get out and bird! Banders and biologists alike went on a birdwatching trip to the central valley to see wintering waterfowl and Sandhill Cranes. The team left west Marin for Cosumnes River Preserve and enjoyed hundreds of Greater White-fronted Geese, Cackling Geese, and Snow Geese in addition to Blue-winged Teal, Cinnamon Teal, Ring-necked Duck, and Ruddy Duck! Everyone tested their abilities to pick out the handful of Ross’s Geese among the Snow Geese. The crew ended their day at Staten Island, San Joaquin County, to watch a couple hundred Sandhill Crane come in to roost for the evening. In all, the group saw a total of 63 species that day, with Sandhill Cranes and Ross’s Geese being “lifers ” for many! You can see our full trip report here.

 

As we geared up to say farewell to the remaining folks on the winter banding cohort and the wintering birds we’d been capturing during February (including Red-breasted Sapsucker, Varied Thrush, and Townsend’s Warbler), we greeted the arrival of our first Allen’s Hummingbird captured at Palo on February 13, 2024.

Thanks to everyone on the crew who made this Winter season one for the books; like the songbirds we so eagerly study, the staff at the Palomarin Field Station are always excited when apprentices return from their own great migrations.

 

 

 

Let’s Do the Numbers:

In 50 days (5933.15 net hours) of mist-netting at Palomarin in November through February, we captured 137 new birds and recaptured 122 previously banded birds. A total of 259 birds of 25 species were caught. Approximately 5 birds were caught per banding day.

 

At our other West Marin banding sites (off-sites), we captured 255 new birds and recaptured 168 previously banded birds. A total of 423 birds of 34 species were caught over 34 banding days during November through February (1863.48 net hours), an average of approximately 12 birds per day.

The highest capture rates at Palomarin and our other West Marin banding sites were on November 1st at Palomarin with 15 birds, and December 1st at Muddy Hollow with 49 birds.

Between November 1st 2023 and February 28th 2024, at Palomarin, the following species were caught in the highest numbers: Ruby-crowned Kinglet (53), Townsend’s Warbler (36), Oregon Junco (36), Hermit Thrush (31), Wrentit (20), and Varied Thrush (15).

In that same time period, across all off-sites, the highest numbers of captures by species were: Song Sparrow (89), Ruby-crowned Kinglet (57), Yellow-rumped Warbler (63 total; 30 Myrtle’s Yellow-rumped Warbler, 25 Audubon’s Yellow-rumped Warbler, and 8 Yellow-rumped Warblers not identified to subspecies), Hermit Thrush (30), and Chestnut-backed Chickadee (30).

 

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.

Early-career bird banders are part of a rigorous training program at Point Blue’s Palomarin Field Station, where they learn to capture birds safely using mist nets and record data on each bird caught. The information collected allows us to better understand how populations of birds are doing and in turn gives us insight into the health of the systems we research. Learn more about our seasonal apprenticeships by visiting the careers page on our website: link.

All birds were captured and handled with appropriate training and permitting.

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