Spatial and temporal variation in breeding parameters of two south‐temperate populations of House Wrens

Abstract

Studies of variation in breeding parameters are often based on temporal analyses of a single population. However, to differentiate between the effects of regional and local factors, neighboring populations with limited interpopulational dispersal need to be compared. We studied two nearby (< 5 km apart) populations of House Wrens (Troglodytes aedon bonariae) at two ranches (Los Zorzales, 10 years; La Esperanza, 13 years) in south‐temperate Argentina to assess the possible effects of regional and local factors on breeding phenology. For each breeding season, we recorded laying dates, clutch sizes, and length of the breeding season, and estimated the reproductive synchrony of first and second breeding attempts. We examined how these breeding parameters were affected by weather, population density, and rates of nest failure. With favorable temperatures during the pre‐reproductive period (September–October), wrens in both populations initiated first breeding attempts earlier. However, ordinal laying dates were also affected by local factors, with wrens at Los Zorzales initiating breeding attempts earlier than those at La Esperanza. We found a spatial correlation in clutch sizes between populations for the 2007–2012 breeding seasons, but clutch sizes of first and second nesting attempts showed low variability. Reproductive synchrony of first nesting attempts varied among years, suggesting an effect of regional factors. However, we detected no synchronization between populations and were unable to identify environmental variables that explained the temporal variation. Ordinal laying dates of second clutches were strongly correlated with the ordinal laying dates of first clutches. We also found that the length of breeding seasons was longer when daily nest mortality rates were lower. Although environmental factors seemed to affect the decision of when to start breeding, pairs with successful first nesting attempts were more likely to initiate second nests, thus affecting the length of the breeding season. The spatial variation and temporal variation of the breeding parameters of House Wrens in our study provide evidence of marked plasticity in their breeding decisions and allowed us to identify local and regional environmental factors related to this variation.

Alarm calls of southern house wrens, Troglodytes aedon bonariae, convey information about the level of risk

“…We studied house wrens nesting at a woodland patch near General Lavalle, Buenos Aires province, Argentina (36°20′S, 56°54′W). The study site comprises a forest dominated by Celtis ehrenbergiana , Scutia buxifolia and Schinus longifolius where we had installed 103 nest boxes that wrens used regularly for nesting (Fernández et al, 2020). In this population, most individuals are colour‐banded (80–95%).…”

It is time to mate: population-level plasticity of wild boar reproductive timing and synchrony in a changing environment

“…A plastic reproductive phenology is a key ecological determinant of animal population sensitivity to changing environments as it represents the time dimension-linkage between reproduction and environment ( Post et al 2008 ; Ogutu et al 2015 ). Such plasticity takes effect on several levels (ovulation, conception, and birth) on both individuals ( Canu et al 2015 ) and populations ( Fernández et al 2020 ). However, it is generally constrained by the reliance on rigid reproductive cues (i.e., photoperiod variations throughout the year, Bradshaw and Holzapfel 2007 ) that do not depend on the environmental conditions.…”

“…The simpler method to investigate the variability of both RT and RS on a population level is to compare the temporal occurrence and duration of an adequate number of breeding seasons with one or more environmental variables ( Ogutu et al 2010 , 2014 ; Fernández et al 2020 ). Unfortunately, this approach requires the condensation of large datasets into 1 observation per year, with a substantial loss of statistical power.…”

Density‐dependent natal philopatry in southern House Wrens

“…Both sexes contribute to nest building and to feeding and defending the young, but only females incubate the eggs and brood the nestlings (Llambias & Fernandez 2009). Clutch size is usually four to five eggs but ranges from three to seven eggs with no difference between first and second broods (Fern andez et al 2020). Females typically re-nest after nest failure and often raise up to two broods per season (Carro et al 2014).…”