Seasonal clutch size variation of multi‐brooded bird species: comparisons between breeding season and latitudes

Abstract

Single-and multi-brooded species of birds differ in their seasonal patterns of clutch size. Single-brooded species start with a maximum clutch size that declines continuously as the season progresses, whereas the clutch sizes of multi-brooded species usually increase to a mid-season maximum peak and then decrease progressively until the end of the breeding season. Previous studies have shown that multi-brooded migrant species present seasonal patterns that are similar to single-brooded species at high latitudes but similar to multibrooded non-migratory species at lower latitudes. We studied the Greenfinch Carduelis chloris and Goldfinch C. carduelis populations in eastern Spain (Sagunto, Valencia) between 1975 and to compare seasonal variations in clutch sizes between years with early and late starts to the breeding season. The period over which clutch sizes increase was longer when the breeding season started earlier. The Goldfinch population showed no pattern of initial increase in clutch size when there was a late start to the breeding season: a late start shortens the season giving them less time to breed, and may also coincide with maximum food availability. Thus, the pattern of single-brooded species was observed. In the Greenfinch population, a trend toward the seasonal pattern of single-brooded species was also observed when the following indices were compared: clutch size increase, modal timing, initial slope and timing of maximum clutch size. We have also compared the seasonal patterns of clutch size of both species in eastern Spain with the patterns observed in Britain. Our results show that for both Goldfinches and Greenfinches, the non-migrant southern populations of Sagunto in eastern Spain do not tend towards a more multi-brooded seasonal pattern of clutch size than the migrant Goldfinches of Britain.Passerine birds use two tactics to maximize their number of offspring per breeding season. In singlebrooded species, the clutch size is at its maximum at the start of the breeding season and declines as the season progresses. Multi-brooded species, however, present a different pattern. Their breeding season is longer and females lay several clutches with a midseason peak of clutch size (Lack 1954, Klomp 1970. Therefore, in multi-brooded species, seasonal reproductive success is determined not only by the productivity of each brood but also by the number of broods raised (Bryant 1979, Desrochers & Magrath 1993. As a consequence, Crick et al. (1993) suggested that multi-brooded species start laying before the optimal moment, which accounts for the increase in clutch sizes until the optimal time, when clutch sizes are the largest. In addition, a tendency to start breeding earlier would be normal as it would allow a greater number of clutches per season. Furthermore, the same species might present both patterns across its distribution range if it is made up of non-migrant as well as migrant populations. The Eastern Bluebird Sialia sialis shows an initial increase in the size of clutches in the southern p...

Breeding biology of the European GreenfinchChloris chlorisin the loquat orchards of Algeria (North Africa)

“…Compared with other studies, the mean clutch size in this study was similar to that reported by Gil-Delgado et al (2005) in Spain (4.4 ± 0.83, n = 370), higher than that reported in Algeria (4.26 ± 0.63, n = 50, Isenmann and Moali 2000;4.09 ± 0.75, n = 37, Kouidri 2013), and significantly smaller to that reported in European countries (4.83 ± 0.03, n = 593, Monk 1954;5.07 ± 0.74, n = 215, Kosinski 2001). Differences between our results and the study of Kouidri (2013), which was conducted at 1593 m above sea level, may be due to a slight decrease of clutch size with increasing altitude.…”

“…The breeding season started two weeks earlier than that reported for Greenfinch by Kouidri (2013) in Algeria and about four to five weeks earlier than in European countries (Monk 1954;Kosinski 2001;Gil-Delgado et al 2005), but it seems that these results are quite similar to those in North Africa (Heim de Balsac and Mayaud 1962;Isenmann and Moali 2000;Isenmann et al 2005). In addition, the beginning of the breeding season varies with latitude and altitude.…”

Latitudinal and seasonal patterns in clutch size of some single‐brooded British birds

“…The r 2 values of the best-fitting multiple regression models vary markedly from 9% (Chaffinches) to 35% (Willow Warblers) and have a mean r 2 value of 17% (Table 4), which is comparable to that found in other studies of intraspecific spatial variation in clutch size , Gil-Delgado et al 2005. A number of general trends emerge from these models.…”

“…Investigations of the interaction between latitudinal and seasonal gradients in clutch size are rare (but see Gil-Delgado et al 2005). However, seasonality increases with latitude, and thus it appears logical that resource availability will decline more rapidly during the breeding season at high latitudes relative to low ones.…”

Breeding patterns of great tits (Parus major) in pine forests along the Portuguese west coast

“…The influence of different geographic areas and habitats on life history patterns has elucidated how climate and habitat act in concert to shape these patterns (e.g. Sanz 1998;Dhondt et al 2002;Gil-Delgado et al 2005). The great tit (Parus major) is a common cavity-nester all over Europe.…”