One key to improved understanding of birds is long-term monitoring in a controlled environment. Unfortunately, many songbird species are reluctant to breed in captivity, limiting the types of studies that can be conducted.
Understanding adaptation to change
Researchers: Sarah Wanamaker, Ellen Ketterson, Allison Byrd, and Adam Fudickar
To augment ongoing bird research, MCB biologists Sarah Wanamaker and Ellen Ketterson are investigating strategies to breed a well-studied songbird—in this case, the dark-eyed junco—in a lab environment. At Kent Farm Research station, researchers are able to control variables that affect birds’ reproductive activity. Since 2000, the team has been experimenting with variables, such as indoor and outdoor housing, population density, temperature, and humidity, to study their effects on birds’ health and reproductive success.
Depending on the year, researchers have:
- isolated birds in pairs, or allowed them to fly freely;
- artificially lengthened daylength or advanced the photoperiod;
- separated birds using visual barriers;
- altered the sex ratio; and
- offered various nesting materials.
While the number of birds and manipulation varied from year to year, however, most years produced somewhere between 0 and 5 young, which often did not survive their first year.
The number of birds has been variable across years but has ranged from 20-50 birds (10-25 pairs). In 2021, researchers had 5 pairs outdoors and 3 pairs indoors. In 2022, they housed 8 pairs outdoors and 3 pairs indoors. Until 2022, all captive breeders had been wild-caught birds, mostly from Mountain Lake Biological Station in Giles County, Va. Now, there are both wild caught and first-generation captive-bred breeders.
Researchers discovered that one of the most important factors for successful junco breeding in captivity is population density. By keeping density low, with no more than 16 birds in one outdoor space, the team has been able to successfully rear 36 young over the past two years. This is a promising increase from previous years, which averaged 0-2 surviving young.
Another major breakthrough was offering more food. Researchers ensured that the birds had access to numerous types of worms every day during breeding season. Researchers also fed mealworms nutrient-dense items in the days before they were fed to the birds, increasing nutrient density. Because nestlings and young fledglings exclusively eat insects, the diet allowed them to thrive.
