Observation
On June 3rd, 2000, at Jurmo bird observatory (59°50'N, 21°37'E), a 2nd calendar-year female flycatcher Ficedula was trapped in a mist-net while ringing migrant passerines. This bird was the only ficedula to be caught during the whole day. In Finland, the Pied Flycatcher (Ficedula hypoleuca) is an abundant breeding species and a common migrant in Jurmo. Collared Flycatcher (Ficedula albicollis) is a rare species with some five annual records in the whole country. So, one is expecting a flycatcher to be a Pied.
While extracting the bird from the net, however, I noted above a greyish tone unfamiliar to Pied Flycatcher, particularly on the sides of the neck, and a large white patch on bases of primaries. I thought the bird in my hand could be a Collared Flycatcher, but blowing the neck-feathers was a disappointment: there were no anchor-shaped markings typical to Collared. Because of the contradictory plumage details I originally identified the bird as a hybrid flycatcher and took it to bird observatory building. At the observatory, three other experienced birders (Jari Helstola, Tarmo Nurmi and Pekka Toola) also saw the bird, which was measured, ringed and photographed. The bird was later released near the observatory, but was not seen subsequently.
Measurements and description
Weight 10,8 g, fat score 0, flight muscle index 2. Bill (skull) 10,0 mm, bill (feathering) 7,7 mm. Wing length (maximum chord) 79 mm.
Wing formula (distances in mm from wing-tip, primaries numbered ascendently):
1 2 3 4 5 6 7 8 9 10
Sec
43 6 0 0 3 10
14 18 20
23
25
The first primary is thus 37 mm shorter than the second primary. The tip of P2 falls between P5 and P6.
Photo 1. Aberrant female Pied Flycatcher (Ficedula hypoleuca), or a hybrid. Jurmo
bird observatory 3.6.2000. Photo: Jyrki Normaja.
Very few hybrid female flycatchers have ever been accepted or even claimed in Finland; most of them certainly remain undetected. However, they certainly exist, because in the nearest breeding area (Gotland island in Sweden) there are many hybrid pairs.
Mild & Shirihai (1994) describe the female hybrids:
"Hybrid female Collared x Pied Flycatchers are extremely difficult to recognise. The majority are so close to on or other of the parents species that they are impossible to separate. In the hand, a few hybrids could arose suspicion by their conflicting morphological and biometric characters, but probably only if the observer has considerable experience of females of both Collared and Pied (see Mild 1993). The hybrids may call like one or other of the parent species, or alternate between Pied's 'pik' call and Collared's 'heeep', but they are never anything in between."
All the following biometric data is given in Mild (1993):
In 2cy Pied Flycatcher, there should be no visible white at the primary bases (n=35). In 2cy Collared Flycatcher, the length of the white patch is from -2 to +4,5 mm (n=47) from tip of longest primary covert in folded wing (- = shorter than the longest primary covert, + = beyond longest primary covert).
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From which primary does the white on the base of outer web occur in 2cy females? |
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P3 |
P4 |
P5 |
P6 |
P7 |
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Ficedula hypoleuca hypoleuca |
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3 % |
66 % |
31 % |
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Ficedula albicollis |
4 % |
37 % |
50 % |
9 % |
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Hybrids |
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25 % |
63 % |
12 % |
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In the Finnish bird, from P4 (weak). |
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Position of the tip of the second primary in relation to P4-P6 (both sexes and all ages combined): | ||||||
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P2=P4 |
P2=P4/P5 |
P2=P5 |
P2=P5/P6 |
P2=P6 |
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Ficedula hypoleuca hypoleuca |
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8 % |
18 % |
74 % |
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Ficedula albicollis |
1 % |
56 % |
33 % |
15 % |
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In the Finnish bird, P2=P5/P6. |
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Important measurements in 2cy female
flycatchers |
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Ficedula h. hypoleuca |
Ficedula albicollis |
Hybrids |
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Wing length |
74-80,5 mm (av77,2, n=40) |
76-84 mm (av83,1, n=603) |
76-80 mm (av78,2, n=12) |
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P2>P1 |
34,9-37,8 mm (n=4) |
40,1-42,4 (n=4) |
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P5<wing tip |
2,7-3,7 mm (n=4) |
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P6<wing tip |
8,8-9,1 mm (n=4) |
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In the Finnish bird, wing length was 79 mm, P2>P1 37 mm, P5<wing tip 3 mm, P6<wing tip 10 mm | |||
The Finnish Rarities Committee decided to ask for the opinion of the
known flycatcher-expert, Swedish Krister Mild. In his reply to Finnish RC he
says (the original text in Swedish is found at the end of this article, for
those wishing to read it without translation):
"In my opinion this 2cy flycatcher can NOT be accepted as a hybrid between Collared and Pied Flycatcher.
To be able to prove a female hybrid in the first place (with other than blood sample), the bird must show many intermediate measurements and plumage details. This individual does not show ANY typical plumage details of the Collared Flycatcher, with the exception of the white patch in the base of primaries being too large for a 2cy Pied Flycatcher. The colour of the mantle, neck-feathers, tertials and upper tail-coverts are like in typical Pied Flycatcher. Rectrices are OK for both Pied and Collared Flycatcher. Some Pied Flycatchers do have some grey on the sides of the neck. However, it has more white in the bases of primaries than I've ever seen on a 2cy Pied Flycatcher (see measurements below).
Wing formula is very much like a normal Pied Flycatcher, and there are no wing formula details which would support Collared. The only abnormal thing is the size of the white patch in the bases of the primaries. I have never seen a 2cy female with this large patch with the white beginning from the outer web of the 4th primary and continuing 3 mm past the primary coverts on the folded wing. This character fits better a Collared Flycatcher. In my opinion, however, this only character IS NOT ENOUGH to prove a hybrid. I would for instance expect to have some contradictory measurements or wing formula. And preferably a blood sample!
This bird can very well be a hybrid, but the possibility of an extremely
aberrant Pied Flycatcher can not be excluded. Theoretically, the plumage also
fits the Iberian race of the Pied Flycatcher, Ficedula hypoleuca iberiae. Please note
that the hybrid females are considerably more uncommon than males, because the
hybrid females have higher mortality than the males. The females are also
usually sterile, as the hybrid males have approximately same mortality and
fertility as Collared and Pied Flycatchers.
Sorry for the negative statement,
Krister Mild"
The original statement form Krister Mild to Finnish Rarities Committee
(in Swedish):
Min åsikt är att denna 2k flugsnapparhona INTE kan godkännas som en
hybrid mellan albicollis och hypoleuca.
För att överhuvudtaget kunna påvisa en hybridhona (med annat än ett
blodprov) måste den fångade fågeln uppvisa ett flertal intermediära mått och
dräktkaraktärer. Denna individ uppvisar INGA typiska dräktkaraktärer för
albicollis, annat än att handpennebasfläcken är för stor för en 2k
hypoleuca-hona. Mantelfärg, nackfjädrar, tertialer och övre stjärttäckare är
tecknade som hos en typisk hypoleuca. Stjärtpennorna passar in både på hypoleuca
och albicollis. Lite grått på halssidorna har även en del hypoleuca. Dock har
den mer vitt på handpennebaserna än jag sett hos någon 2k hona hypoleuca (se
mått nedan).
Vingformeln är mycket lik den hos en helt normal hypoleuca, och det finns
inga vingformelkaraktärer som stöder albicollis. Det enda som avviker från en
normal hypoleuca är storleken på handpennebasfläcken. Jag har aldrig stött på en
2k hona som uppvisar en så stor fläck och där det vita börjar redan på
ytterfanet av 4 samt att når så långt som 3 mm utanför handpennespetsarna på den
hopslagna vingen. Denna karaktär passar bättre hos halsbandsflugsnappare. Dock
anser jag att denna enda karaktär INTE RÄCKER som bevis för hybrid. Jag ville
exempelvis också gärna ha motstridiga mått/vingformel. Och helst blodprov!
Denna fågel kan mycket väl vara en hybrid, men en extremt avvikande
hypoleuca kan inte helt uteslutas. Rent teoretiskt passar dräkten hos denna
fågel också in på en F. hypoleuca iberiae. Observera att hybridhonor är avsevärt
mer ovanliga än hybridhannar, beroende på att hybridhonor har en högre
mortalitet (och är vanligen sterila) medan hybridhannar har ungefär samma
mortalitet och fertilitet som rena halsbandsflugsnappare respektive svartvita
flugsnappare.
Jag är ledsen för det "negativa" beskedet!
Krister Mild
Based on the statement by Krister Mild, the Finnish Rarities Committee
considered the identification unproven and thus rejected the
record.
When suspecting a (female) hybrid flycatcher, always take as many measurements as possible. Without a DNA-sample, a single character of the other species – although it may be outside the known variation of the other species – may not be enough to PROVE a hybrid (and get it accepted by the RC).
Whether the Finnish bird actually was a hybrid or not, is a question which will probably never be answered. However, I feel it is important to bring to common knowledge the looks of this bird and the fact that the identification of female flycatchers is even more complicated than often is being thought.
Mild,
K 1993: Die Bestimmung der europäischen schwarzweißen Fliegenschnäpper Ficedula. Limicola
7:222-276.
Mild,
K & Shirihai, H 1994: Field Identification of Pied, Collared and
Semi-collared Flycatchers. Part 2: females in breeding plumage. Birding World
7:230-240.
Svensson,
L 199#: Identification Guide to European Passerines.
Stockholm.
Photo 2. Aberrant female Pied Flycatcher (Ficedula hypoleuca), or a hybrid. Jurmo bird observatory 3.6.2000. Photo: Jyrki Normaja.
Photo 3. Female Collared Flycatcher (Ficedula albicollis). Jurmo bird observatory, 20.5.1998. Photo: Jyrki Normaja
