The spring banding season of 2019 marked the 20th year of banding birds at Chico Basin Ranch. The first two years were shorter pilot seasons and in 2002 the station operated its first full length season. Since that time, the banding station at Chico Basin Ranch has established itself as one of the most diverse (and busy!) banding stations in Colorado. To date, an incredible 155 species have been banded here, including many eastern species rarely seen this far west.
This spring season was characterized by a mix of wet weather and several large migration pulses. Spring migration in birds tends not to occur at a steady pace but rather is defined by ‘pulses;’ when weather factors such as temperature, wind speed, and wind direction align to produce favorable migration conditions. In such conditions, migrating birds can be found in incredible densities for just a day or two at a time, concentrated in places with good foraging opportunities such as the banding station area in the Holmes Grove.
A young female Northern Parula.
This season our nets opened on April 22nd and ran through May 23rd (closed on Sundays). We banded a total of 585 birds of 50 species this spring (see Table 1 below for a breakdown by species). While this is below our spring season average, its actually quite a high total if we take into account the ‘total effort’ for the season. In addition to recording data on the birds themselves, banders also track the daily effort at a banding station. That is, how many nets were open for how many hours each day. When weather conditions are poor (rainy, windy, snowy) nets are closed to ensure the safety of the birds. This spring we had more net closures than usual due to the many rain storms and generally wet weather. However, when the station was able to be open the capture rates were quite high. In other words, it was a wet season but very busy when the weather was good!
Our most commonly banded bird was the Swainson’s Thrush, with 114 newly banded this spring. This has been our most commonly banded bird nearly every spring, losing out narrowly to House Wrens in 2005 and Lincoln’s Sparrows in 2013. Among our more unusual captures was a single female Northern Parula as well as a female Black-and-White Warbler. We also banded two Canyon Towhees, a species that is not unusual in the area but is rarely caught in our nets. Prior to this spring, only 2 other Canyon Towhees had been banded since the station began in 2000.
A male Western Tanager.
We also had a total of 16 birds that were banded in a previous season and returned again this year. These returning birds were comprised of 7 American Robins, 2 Brown Thrashers, 1 Song Sparrow, 1 Gambel’s White-crowned Sparrow, and 5 Bullock’s Oriole. Perhaps our most exciting capture of the season (although we didn’t know it until digging through the data post-season) was a Bullock’s Oriole that was previously banded, though not by us! Data from this bird has been submitted to the national banding database at the Bird Banding Laboratory in Maryland, and we are waiting to hear where and when it was originally banded. Recaptures of birds banded elsewhere are quite rare (less than one a season) and collectively tell us a lot about bird migration, helping to connect migratory stopovers with breeding and/or wintering grounds.
Overall it was a fun (if wet!) banding season with some busy days and exciting birds. Thank you to all the visiting birders and educational groups that help make the banding station possible and a big thank you to Genevieve Day, our lead bander this spring.
By Colin Woolley. To find out about volunteer opportunities at the banding station, please contact colin.woolley@birdconservancy.org.
Table 1: Species breakdown of newly banded birds during Spring of 2019. The average of previous full seasons is also presented for comparison.
| Species | Newly Banded in 2019 | Avg of Previous Years
(2003-2018) |
| Downy Woodpecker | 2 | <1 |
| Ladder-backed Woodpecker | 2 | <1 |
| Western Kingbird | 2 | 3 |
| Eastern Kingbird | 2 | 1 |
| Olive-sided Flycatcher | 1 | <1 |
| Western Wood-Pewee | 2 | 4 |
| Willow Flycatcher | 2 | 3 |
| Least Flycatcher | 9 | 10 |
| Dusky Flycatcher | 10 | 12 |
| Cordilleran Flycatcher | 1 | 1 |
| Plumbeous Vireo | 1 | 4 |
| Warbling Vireo | 2 | 6 |
| Blue Jay | 4 | 8 |
| House Wren | 26 | 54 |
| Blue-gray Gnatcatcher | 2 | 2 |
| Golden-crowned Kinglet | 1 | <1 |
| Ruby-crowned Kinglet | 14 | 7 |
| Swainson’s Thrush | 114 | 148 |
| Hermit Thrush | 46 | 54 |
| American Robin | 12 | 12 |
| Gray Catbird | 20 | 18 |
| Brown Thrasher | 4 | 7 |
| House Finch | 3 | 3 |
| American Goldfinch | 2 | 10 |
| Green-tailed Towhee | 1 | 5 |
| Spotted Towhee | 22 | 17 |
| Canyon Towhee | 2 | <1 |
| Chipping Sparrow | 4 | 35 |
| Vesper Sparrow | 1 | <1 |
| Lincoln’s Sparrow | 51 | 52 |
| White-throated Sparrow | 1 | 1 |
| “Gambel’s” White-crowned Sparrow | 9 | 37 |
| “Pink-sided” Dark-eyed Junco | 1 | 2 |
| Yellow-breasted Chat | 12 | 5 |
| Bullock’s Oriole | 25 | 12 |
| Red-winged Blackbird | 1 | 3 |
| Brown-headed Cowbird | 2 | 2 |
| Ovenbird | 3 | 5 |
| Northern Waterthrush | 4 | 2 |
| Black-and-white Warbler | 1 | 1 |
| Orange-crowned Warbler | 30 | 22 |
| MacGillivray’s Warbler | 31 | 25 |
| Common Yellowthroat | 6 | 10 |
| American Redstart | 3 | 1 |
| Northern Parula | 1 | <1 |
| Yellow Warbler | 27 | 28 |
| “Audubon’s” Yellow-rumped Warbler | 23 | 41 |
| “Myrtle” Yellow-rumped Warbler | 18 | 20 |
| Wilson’s Warbler | 12 | 13 |
| Western Tanager | 9 | 10 |
| Rose-breasted Grosbeak | 1 | 1 |