For a number of years it has been possible to analyse DNA to determine the sex of captive birds - when this is difficult to do by simply looking at them. Small quantities of blood, or plucked feathers provide the DNA. These same techniques can also be used to separate closely related bird species. More recently old feathers, or the snipped off ends of feathers have been used to the same ends, and in some cases it has even been possible to use feathers from old museum specimens.
Finding Unusual Species by DNA Analysis
In 2001 a strange skua (seabird) was found at St.Agnes on the Scilly Isles. The bird was sick and while it was being cared for a few feathers were plucked and sent to Glasgow University for DNA analysis.
The result surprised birdwatchers because it was found that the bird was a 'Falkland Skua' - a bird which 'should not' have been in the northern hemisphere.
In 2002 another skua was found on Aberavon Beach in Wales, and similar testing gave the same result, and added a new species to the European bird list.
Since skuas are sometimes difficult to identify by sight these findings suggest that is difficult to know how many of these southern birds wander into the Atlantic each year.
Identifying Extinct Birds in Museums
Research workers in New Zealand have been able to find four different species of moa (extinct flightless birds) from the feathers thought to be 2,500 years old.
They were then able to look at museum specimens to identify these birds as the stout-legged moa, heavy-footed moa, upland moa, and the South Island giant moa.
Using information from pigments still left in these feathers they went on to reconstruct the appearance of these birds.
Professor Alan Cooper of the Australian Centre for Ancient DNA says: 'this finding suggests it may be possible to reconstruct the appearance of other extinct birds using feathers from fossil deposits'.
Plucking and Clipping Bird Feathers, and Using Blood Samples for DNA Analysis
The Journal of Avian Biology carried a paper in 2005 (Horvath, Martinez-Cruz et al) that suggested that whole feathers could provide sufficient DNA in the blood clot located in the superior umbilicus of the feather shaft to make testing easier than using clippings. (See article image where 1 = Vane, 2 = Rachis, 3 = Barb, 4 = Afterfeather, and 5 = Hollow shaft). This technique works well with living birds, and it can also be used for museum specimens.
McDonald and Griffith (2011) have had a good look at all the techniques available for obtaining DNA samples from living birds, and they point out that blood provides: 'large yields of high quality DNA that facilitates archival storage of samples in a manner that the destructive sampling of feathers cannot'.
They argue that: 'the practise of feather plucking or clipping should be strongly discouraged on both scientific and ethical grounds'.
So the jury is still out! Blood and feathers can both be used to provide the DNA for research work, but which method is better and more ethical when working with rare birds in the field?
Sources:
- Giant Moa Rebuilt Using Ancient DNA From Prehistoric Feathers, ScienceDaily, 2009.
- An overlooked DNA source for non-invasive genetic analysis in birds, Marton B. Horvath, Begona Martinez-Cruz, Juan J. Negro, Lajos Kalmar and Jose A. Godoy, Journal of Avian Biology, 2005.
- To pluck or not to pluck: the hidden ethical and scientific costs of relying on feathers as a primary source of DNA, Paul G. McDonald, Simon C. Griffith, Journal of Avian Biology, 2011.
