A fairly huge population, about 50 percent, of birds along the coast of Maine, New Hampshire and Massachusetts are actually half-bred Saltmarsh and Nelson's Sparrows, a new study found.
A team of international researchers led by the University of New Hampshire's (UNH) Agricultural Experiment Station conducted a field study to observe the feathered fellas along these hybrid zones and further identify them through DNA testing. Looking at the species alone, the team found that the lines between the Salmarsh Sparrow and the Nelson's Sparrow are blurry.
According to the researchers, when species that are closely related with each other interbreed, their offspring backcross either of the parent species. When it continuously happens, a whole population of cross-bred species makes up the hybrid zone. In a paper published online in the journal The Auk: Ornithological Advances, the researchers discuss specifically the relationship of the two species of sparrow along these hybrid zones.
In their study, the researchers looked at the birds in 34 sites that covered about 50 kilometers along the hybrid zones of New Hampshire, Maine and Massachusetts and according to physical appearance, identified the which species they belonged to. Plumage, body size and bill size were used to identify them as either a Saltmarsh Sparrow, a Nelson's Sparrow or a hybrid. Then, they took blood samples to confirm if identification through appearance was accurate, through DNA analysis.
The results of DNA testing revealed that hybridization of the Saltmarsh and Nelson's Sparrows lead to complex combinations of the offspring's plumage traits, making it difficult to identify a pure-breed from a hybrid.
"This also means that it is challenging to monitor the abundance/distribution of hybrids within natural populations without collecting genetic data," added UNH researcher Jennifer Walsh, highlighting that both the Saltmarsh and Nelson's Sparrows are prioritized as high conservation species in the Northeast. The Saltmarsh Sparrow is actually even globally considered vulnerable to extinction. These species could be better managed through hybrid identification, as well as matching, the researchers point out.
The researchers further note that to ensure a secure future for the Saltmarsh and Nelson's Sparrows, it is important to first ascertain "which is which," and that can only be confirmed by genetic data through DNA sampling.
Under the mentorship of UNH's Adrienne Kovach, Walsh conducted the study as part of her doctoral research. They collaborated with experts from the University of Delaware, University of Maine and the US Fish and Wildlife Service, with the authors, members of the academic, government and nonprofit research group Saltmarsh Habitat and Avian Research Program
Photo: Christopher Eliot | Flickr
