Occurrence of twin embryos in the eastern bluebird
- Published
- Accepted
- Subject Areas
- Ecology, Zoology
- Keywords
- eastern bluebird, Pennsylvania, Sialia sialis, twinning, double-yolked egg, citizen science
- Copyright
- © 2014 Bailey et al.
- Licence
- This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
- Cite this article
- 2014. Occurrence of twin embryos in the eastern bluebird. PeerJ PrePrints 2:e186v1 https://doi.org/10.7287/peerj.preprints.186v1
Abstract
We report the first record of presumed twinning in eastern bluebird (Sialia sialis) and provide a review of all previously reported twinning events in wild birds. A nest containing twin eastern bluebird nestlings was monitored in 2013 in central Pennsylvania and reported to the Cornell Lab of Ornithology’s NestWatch program, a national program where volunteers submit data on wild nesting birds. A presumed double-yolked egg of a free-living eastern bluebird pair hatched successfully, and twin nestlings lived for 11 days in a nest box shared by three siblings. Due to the rarity of twinning in wild birds, engaging the public to monitor large numbers of nests is the most likely approach to documenting twinning in wild populations, and citizen science provides the infrastructure for individuals to share observations.
Supplemental Information
Cases of twinning in wild birds.
We found 14 documented cases of twinning for 13 species of free-living birds. Examples are known from either dissected unhatched eggs (n = 10) or from unassisted, hatched eggs where nestlings exceeded clutch size (n = 4).
Image of bluebird clutch before hatching.
On 28 June 2013, an eastern bluebird (Sialia sialis) nest was observed containing one relatively large egg (bottom right) and three normal-sized eggs in State College, Pennsylvania.
Photo taken on hatching day with one egg and four nestlings.
On 1 July 2013, likely the day of hatching, four nestlings were observed with one unhatched egg.
Photo of five nestlings.
Five eastern bluebird (Sialia sialis) nestlings were present on 5 July 2013.
Image of three live and two dead eastern bluebird nestlings.
At 8:15 am on 12 July 2013, the nest contained three live nestlings with two dead nestlings below them.
Image of one eastern bluebird carcass.
On 12 July 2013, one carcass was found outside the nest box. It showed no obvious signs of structural problems or trauma.
