Hybridization and apparent hybridization between meadow pipit (Anthus pratensis) and water pipit (A. spinoletta).

Abstract

Occasionally, even a single breeding event may provide significant biological information, of which the present report of a pairing between a female meadow pipit (Anthus pratensis) and a male water pipit (A. spinoletta) may be a good example. Events of mixed-species pairing appear to be relatively common in birds (ARNOLD 1997). However, only rarely has researchers investigated whether such pairings actually results in the production of hybrid offspring. In a study of hybridization between collared flycatchers (Ficedula albicollis) and pied flycatchers (F. hypoleuca), VEEN et al. (2001) showed that females involved in mixed-species pairs often have extra-pair copulations (EPCs) with conspecific males, and that these extra-pair males sire a significant proportion of the nestlings. Accordingly, in these species the rate of actual hybridization is much lower than the frequency of heterospecific pairs would seem to imply. Here we report, to our knowledge, the first incidence of mixed pairing between a meadow pipit and a water pipit. Applying sequence analysis of two autosomal, nuclear introns, we show that only one of the offspring of the heterospecific mating event has a hybrid genotype. The other two offspring have genotypes similar to their mother, suggesting that they are sired by a male conspecific with the female. This result provides further evidence that heterospecific pairing and hybridization are not equivalent phenomena. We suggest that molecular methods should preferentially be used in cases of suspected hybridization. If EPCbehaviour were particularly common in such cases, as would seem likely, rates of hybridization and possibly also male hybrid fitness would tend to be over-estimated in observational studies. The meadow pipit and the water pipit are small monogamous passerines that build their nests on the ground in open habitats, mainly in Central Europe alpine ecosystems. Songs of the two species are rather similar, but the water pipit sings louder with more musical and tinkling notes. There are apparent differences in plumage characters between the two species. The meadow pipit is olive-brown and streaked above, grey-white below and spotted and streaked on chest and flanks. The water pipit has slightly streaked greyish-brown upper parts and dull white under parts with pale buff-pink wash from throat to mid-belly. The first author has studied pipit populations on alpine meadows 1350–1491 m above sea level in the Jeseniky Mountains (Czech Republic, 50°04 N, 17°14 E) since 1986. In total, 84 meadow pipit pairs were caught during 1996–2001. The stated event is the first incidence of a mixed species pairing during the study period.