Browsing by Author "Bolton, Mark"
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- Potential flight range of Snow Buntings Plectrophenax nivalis occurring in the Azores in late March : a first analysis.Publication . Bolton, Mark; Medeiros, Renata; Fraga, HelderIt has been known for many decades that Snow Buntings occur with some regularity in the Azores archipelago in winter, with flocks numbering up to 20 individuals on occasion. The majority of records are from the islands of Corvo and Faial. The origin and fate of these individuals is unknown and it is unclear whether the regular occurrence of such groups represents a wintering strategy, or rather, whether these birds have been blown off the course of their usual migration route. Seven individuals from a flock of ten Snow Buntings known to have been present on the island of Faial between 20th March and early May 2000 were trapped on March 30th 2000. Plumage characteristics indicated they were of the Greenland P.n. nivalis race. Measurements of body mass indicated that the fat reserves of these individuals were similar to those of Snow Buntings wintering in Scotland U.K. at the same time of year, just prior to departure to the breeding grounds. However the calculated potential flight range of the individuals from Faial varied from 500 km to 1.800 km, averaging 1.150 km for females and 1.640 km for males. Whilst these average ranges would be sufficient to make continental landfall if the birds followed an easterly route, such a heading is considered improbable, given their racial characteristics. The calculated energy reserves would be insufficient to sustain continuous flight on a northerly course to continental landfall. The presence of potentially suitable breeding habitat on the neighbouring island of Pico is highlighted.
- Reduced population size does not affect the mating strategy of a vulnerable and endemic seabirdPublication . Nava, Cristina; Neves, Verónica C.; Andris, Malvina; Dubois, Marie-Pierre; Jarne, Philippe; Bolton, Mark; Bried, JoëlBottleneck episodes may occur in small and isolated animal populations, which may result in decreased genetic diversity and increased inbreeding, but also in mating strategy adjustment. This was evaluated in the vulnerable and socially monogamous Monteiro's Storm-petrel Hydrobates monteiroi, a seabird endemic to the Azores archipelago which has suffered a dramatic population decline since the XVth century. To do this, we conducted a genetic study (18 microsatellite markers) in the population from Praia islet, which has been monitored over 16 years. We found no evidence that a genetic bottleneck was associated with this demographic decline. Monteiro's Storm-petrels paired randomly with respect to genetic relatedness and body measurements. Pair fecundity was unrelated to genetic relatedness between partners. We detected only two cases of extra-pair parentage associated with an extra-pair copulation (out of 71 offspring). Unsuccessful pairs were most likely to divorce the next year, but genetic relatedness between pair mates and pair breeding experience did not influence divorce. Divorce enabled individuals to improve their reproductive performances after re-mating only when the new partner was experienced. Re-pairing with an experienced partner occurred more frequently when divorcees changed nest than when they retained their nest. This study shows that even in strongly reduced populations, genetic diversity can be maintained, inbreeding does not necessarily occur, and random pairing is not risky in terms of pair lifetime reproductive success. Given, however, that we found no clear phenotypic mate choice criteria, the part played by non-morphological traits should be assessed more accurately in order to better understand seabird mating strategies.