The Annual Cycle of the Azores Bullfinch, Pyrrhula Murina Goldmangoldman,, 1866 (Aves:(Aves: Passeriformes)
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THE ANNUAL CYCLE OF THE AZORES BULLFINCH, PYRRHULA MURINA GOLDMANGOLDMAN,, 1866 (AVES:(AVES: PASSERIFORMES) JAIME A. RAMOS RAMOS, J.A.lA . 19941994.. The annual cycle of the Azores bullfinch, Pyrrhula murina Goldman, 1866 (Aves: Passeriformes).Passeriformes). Arquipe'lago.Arquipélago. Life and Marine Sciences 12A:l2A: 10101 1-109.-109. Ponta Delgada.Delgada. ISSNIS SN 08700870-685-685 1.I. The annual cyclecyc\e of the AzoresAzores bullfinch or PriBlo,Pri ôlo, Pyrrhula lI1urina,murina, is described. This bird breeds from June to August, when food abundance is high, and starts moulting in September. Seasonal variations in body weight and fat scores were small. The annual September. Seasonal variations in body weight and fat scores were small. The annual mortality is probably less than 60%. The median monthly group size was always one or two. Overall, it presents a strongstrong seasonal pattern similar to that of western European Pyrrhula,Pyrrhula, but with slightsl ight variations. These should be an environmental correlate ofor the oceanicoceanic temperatetemperale climate of S. Miguel island. RAMOS, J.A.lA . 1994.1994. Ciclo anual do PriBloPriôlo A~oreano,Açoreano, Pyrrhula nzurinamurina Goldman, 1866 (Aves: Passeriformes).Passeriformes). Arquipe'lago.Arq uipélago. CiSnciasCiências BioldgicasBiológicas e Marinhas 12A:l2A: 101101-109.- 109. Ponta Delgada.Delgada. ISSN 0870-6850870-685 1.1. Descreve-seDescreve-se o ciclo anual do PriBlo,Priôlo. Pyrrhula miwina.1/1IIrina. Esta ave nidifica de Junho a Agosto, quando a abundâncabundbciaia de aliment0alimento éC elevada.elevada, e comeGacomeça a muda de penas em Setembro.Setembro. O0 peso e o indiceindíce de gordura apresentaram variagiesvariações sazonais reduzidas. A mortalidade anual é provavelmente menos de 60%. O grupo de aves observadas em cada mortalidade anual C provavelmente menos de 60%. 0 grupo de aves observadas em cada m&smês apresentou sempre uma mediana de um ou dois.dois. De urnum mod0modo geral, o PriBloPriôlo apresenta um padrgopadrão sazonal semelhante ao de outros Pyrrhula da Europa Ocidental.Ocidental, embora com ligeiras varia~6es.variações. Tal facto deveriideverá estar relacionado com o clima temperado ocednicooceânico de S. Miguel. Jaime A. Ratnos,Rall1os, Edward GreyCrey Institute of Field Ornithology,OmitllOlogy, Zoology Department, Oxford, OXIOX1 3PS, England; Present addressaddress:: DepartamenloDepartall1ento de Oceanografia e Pescas, Universidade dos Apores,Açores, PT-9900PT-9900 Horta, Agores,Açores, Portugal.Portugal. INTRODUCTION is not known whether their annual cycle resembles that of tropicaltropical montane forest birds. Physiognornically,Physiognomjcally, Azorean cloud forests This may not be expected because, for instance, resemble tropical montane forests (HAGGAR seasonal variations of daylength in the Azores 1988) and seasonal variations in temperature and are much more pronouncedpronounced than those of the water regime are small (SJOGREN 1984)1984).. tropics. The evaluation of this question would MOREAU (19(1950) 50) and SERLE (1981) observed lhatthat provide a primary step in understanding the breeding is seasonal in tropical montane forests.forests. ecology of terrestrial birds in these native forests.forests . For lowland forests, however, they were not able Here, the annual cycle of the Azores (or S.S. to define an universaluniversal breeding season, although Miguel) bullfinch or Priôlo,PriGlo, Pyrrhula murina, is most familifamilieses had a preferred nesting season. No reported.reported. This species is the only endemic bird information is available on the ecology of species of the archipelago (RAMOS 1993).1993). It is Azorean cloud forestforest passerines. For example, it also of crucial importance 00on practical grouodsgrounds 101 because this bird, with a population of about 100 Birds were examined for differences between pairs (BIBBY& CHARLTON,1991), is restricted to male and female plumage, for presence of a the native cloud forest in eastern S. Miguel brood patch, presence or absence of primary (BIBBY& CHARLTON1991; BIBBYet al. 1992; moult, fat score (0 to 4 according to SPENCER RAMOSin press a). The results reported here are 1975), odd marks or injuries and presence or part of a wider research programme on the absence of throat pouches. They were also ecology of the Azores bullfinch carried out colour-ringed, weighed with a 50 g Pesola spring between 1991 and 1993. balance and measured for wing-length, tail- Both breeding and moulting are energetically length, bill-length, bill-depth, tarsus and total costly and are expected to occur when food is head, according to SVENSSON(1984). abundant (LACK1966; PERRINS1970). Although Sexes were indistinguisable in the field. In insular habitats can be regarded as relatively hand, some birds could be sexed by colour equable throughout the year when compared with differences. In males the abdomen and flanks similar mainland areas, these activities still often were suffused with a reddish-tawny tinge as present a strong seasonal component (SNOW& stated by GOODWIN(1985) and there was never a SNOW1964; DIAMOND1980; GREIG-SMITH1980; brood patch. When these criteria were used for BROOKE1985). Generally, the distribution and sexing, a sample size of 22 males (with reddish abundance of food are expected to influence tinge) and 28 females (with brood patch) where overall seasonal rhythms of birds (WIENS1989) obtained. A further 23 birds could not be sexed and will be used here as a basis for an by these methods. From these 23 birds, 12 could examination of seasonal activity patterns. be sexed because they were seen paired with ringed birds of known sex. The traditional This paper provides information on annual method of ageing bullfinches, Pyrrhula pyrrhula, cycle events and, to a lesser extent, the colour differences in their greater coverts population dynamics of the Azores bullfinch. The (NEWTON1966a) was difficult to apply to the following questions were asked: (1) Do breeding Azores bullfinch because adults have buffish and moulting show seasonal occurence and are edged coverts too, unlike the more grey mainland they correlated with food abundance? (2) Are bullfinches. Therefore, for the analysis of overall mortality levels related with food resource mortality rates, it was not attempted to abundance? distinguish between first years and older birds. Recruitment into the population was METHODS estimated by counting the number of juveniles (with brown heads) during walks along routes (marked in the main distribution area of the bird) The study area is described in full elsewhere made every ten days. To assess mortality rates, (E~IBBY& CHARLTON1991; BIBBYet al. 1992; colour-ringed birds were sought widely along all RAMOS 1993). It is a mountainous district in marked routes. eastern S. Miguel with densely vegetated steep Plant species in the study area were examined ground; native forests being present above 400- every month and their phenologies noted. 500 m. Changes in the abundance of foods taken by the Mist netting was carried out at several sites Azores bullfinch (see also RAMOS in press a) both within and at the edge of the Laurel forest. were evaluated by counting the number of seed Nets were placed at feeding sites, especially on heads or fruits of individual food plants in 40 x patches of Polygonurn capitaturn and Leontodon 5m transects at the stations of three routes, at low filii, up to four days a week. (300 m), mid (500 m) and high (700 m) altitude. RESULTS Breeding and moult. The first female with a brood patch was caught on the 10th of June, about three weeks after fresh P.capitatum seeds (a preferred herbaceous seed in summer, BIBBY et al. 1992; RAMOSin press a) became available. The birds' behaviour in late April, May and early June indicated pre-breeding activity. The male's dance and bill caressing (HINDE 1955; NICOLAI 1965) were common in May and early June; a twig display was observed in late April and courtship feeding (see NEWTON 1972) was commonly seen in late May and early June. In the last week of May two birds were seen flying with dry twigs in their beaks. In 1992 two nests were found. The first, on Fig. I. Seasonal pattern of nesting, shown by the the 6th of July, was being built. Two birds were percentage of females with brood patch in 10 day watched for two hours on two consecutive days. periods. Numbers above bars indicate the total They were seen to be carrying twigs, stems of dry number of females caught. Data from 1991 and grass and moss. No eggs were laid in this nest. 1992 were combined. It should be noted that birds The second, found on the 26 of July, had one were difficult to sex (see text). This may be important to explain the decrease in the chick of approximately 10-12 days old. Twelve percentage of females with brood patch in July, faecal sacs (see NEWTON1967) were present on when, presumably, the whole population should the edge of the nest. The first nest was located be breeding. Some of these birds could actually be within a short plantation (< 5 m height) of males. Cryptomeria japonica and the second within Clethra arborea and native forest but both were the 10th of June with a brood patch, and again on placed on a C. japonica tree at about 3 m height. the 3rd of August still with a brood patch, Nests were alike, consisting of an outer layer of perhaps suggests a second breeding attempt by twigs of C. arborea and Erica azorica and an some birds. A small proportion of birds could inner layer of rootlets, grass and a few bits of still be breeding in early September, but no adults moss. were caught which verified this (Fig. 1). Although breeding commenced in June a The progressive appearance of juveniles into significantly higher proportion of birds started the population (% of juveniles seen during route only in July (X2=10.06 P<0.001, df=l with Yates' walks) is shown in figure 3. Juveniles reached correction) (Fig.