That’s what they are starting to call it…
Headlines on the 1st winter female Flycatcher, trapped at Spurn, East Yorkshire on 3oth August 2010. Remained until 1st September. I have had some fantastic help from Johan T., Simon C. and Holger S. Here it is again:
And the news update:
From Holger Schielzeth on DNA
“It is certainly NOT a Pied Flycatcher nor an F1 (first generation) hybrid. Since there does not seem to be any strong reason that suggests a backcross and knowing that they are rare, I think it is pretty safe to identify the Spurn bird as a Collared Flycatcher.”
From Johan on Gotland
“all I have seen indicates a typical Collared fly.”
“But I am rather convinced of that your Spurn-bird is a pure Collared fly.”
From Simon Christiansen (Ottenby Bird Observatory).
“…before the DNA was done. We (SC and Magnus Hellström) discussed the bird a little bit and we came to the conclusion that it most likely fit a Collared”
Effectively ALL British Collared Fly records could have Pied Fly genes in them as:
“You can never exclude F1 or backcross birds by just watching the birds because F1′s and backcrosses can have the original plumage of one of the species (Pied fly or Collared fly).” (Johan T)
Here some photos of 1st winter Collared Flycatchers (unsexed) from Oland Bird Observatory all taken in the second half of August (in either 2009 or 2010). Some look easier than others!
A more detailed statement on the DNA
The bird was successfully typed at 4 microsatellite loci (Fhu1, Fhy304, Fhy401 and Fhy403). Each locus has two alleles, because each individual carries two chromosomes (‘alleles’ are the states of the locus at the two chromosomes). Microsatellites are repeat sequences of variable length and the alleles are scored for their length in basepairs (bp).
Pure-bred individuals would show only alleles of their own species at all loci, F1 hybrids would have exactly one Collared and one Pied allele at each locus and back-crosses could have a wild mixture (but 1/4 of the alleles are expected to be of the other species, on average).
Back-crosses are rare, since females hybrids are infertile and males hybrids have reduced fertility (Veen et al. 2001. Hybridization and adaptive mate choice in flycatchers. Nature 411:45-50), but they nevertheless do occur.
At two loci (Fhu1 and Fhy401), the Spurn bird had both alleles from Collared (Fhu1: two alleles 123 bp, Fhy401: two alleles 306 bp). Hence, it can’t be a Pied and it can’t be a F1 hybrid. It could still be a backcross. In a backcross (F1 hybrid x Collared), we would expect 1/4 of all alleles to be Pied alleles (on average!). If it was a backcross, the chance to find four Collared alleles at two loci would be 25%, since the hybrid parent (with one allele from each species at all loci) would have had to inherit its Collared alleles at both loci with a 50% chance for each locus (0.5 x 0.5 = 0.25).
At the other two loci (Fhy304 and Fhy403), the Spurn bird had alleles from the range of overlap between Pied and Collared (Fhy304: two alleles 246 bp, Fhy403: alleles 192 bp and 196 bp). Hence, based on these two loci, it could be Collared, Pied or a hybrid. Unfortunately, I didn’t get allele frequency data so far, so I don’t know if the allele that we found are more common in Pied or in Collared and thus more indicative of the one species or the other. Although for these two loci the data are indecisive, they do not contradict the identification as a Collared.
The samples were genotyped at a sexing locus, too, but the DNA amplification didn’t work. Hence, we can’t say if the bird was a male or a female. We also tried to get genotypes for more microsatellite loci for species identification, but again we did not got good results.
Altogether, the bird is certainly not a Pied and not a F1 hybrid. The odds for it being a pure Collared versus backcross is 1:0.25 (based solely on the genotypes at Fhu1 and Fhy401). Since there does not seem to be any strong reason that suggests a backcross and knowing that they are rare, I think it is pretty safe to identify the Spurn bird as a Collared Flycatcher.
Department of Evolutionary Biology
Evolutionary Biology Centre