Factors affecting fledgling output of great tits, Parus major, in the long term

Abstract

Factors affecting fledgling output of great tits, Parus major, in the long term.-Fledgling production has often been used as an estimator of avian reproductive success, and it is conditioned by factors affecting offspring development and/or survival during the nesting period. We aimed to determine which predictors influenced fledgling output among a set of basic breeding parameters and local temperature data collected over 25 years in a Mediterranean great tit, Parus major, population, using an information-theoretic approach for model selection. Of the studied variables, the number of hatchlings per nest was the single-most important predictor influencing fledgling production, with larger broods eventually yielding more fledglings, although mass prior to fledging may have been compromised. This result suggests an overall good adjustment between brood size and resource availability in the studied population. ResumenFactores que afectan a la producción de volantones en el carbonero común, Parus major, a largo plazo.-La producción de volantones ha sido frecuentemente utilizada para estimar el éxito reproductor de las aves y está condicionada por factores que afectan al desarrollo de los pollos, a la supervivencia o a ambos durante su estancia en el nido. Nuestro objetivo en este trabajo fue determinar los factores predictores que influyen en la producción de volantones a partir de un conjunto de parámetros reproductivos básicos y temperaturas locales recopilados durante 25 años en una población mediterránea de carbonero común, Parus major, haciendo uso de criterios de información para la selección de modelos. De las variables estudiadas, el número de huevos eclosionados por nido resultó ser el factor predictor con mayor influencia en la producción de volantones, de tal forma que las puestas más grandes originaron más volantones, si bien el peso de los pollos antes de abandonar el nido podría haberse visto comprometido. Este resultado sugiere que hay un buen ajuste general entre el tamaño de puesta y la disponibilidad de recursos en la población estudiada.Palabras clave: Producción de volantones, Supervivencia en el nido, Tamaño de puesta, Estudio a largo plazo

Rewriting The Ugly Duckling tale: a Eurasian tree sparrow reared among great tits

“…Another unusual observation is that after only 66 % of the eggs had hatched, two additional nestlings died (probably from starvation) on their first days of life. This means that the breeding success (number of fledglings per egg laid) of the great tit was 44 %, an extremely low figure for first clutches in this study area (Rodríguez et al, 2016). Possibly, the sparrow chick, being larger, could have taken up a significant part of the food provided by the parents, possibly accounting for the deaths of its 'half-siblings' shortly after hatching.…”

“…Once dumped, the sparrow egg was incubated and hatched successfully. It is not known to which degree this interfered with the normal incubation behaviour of the great tit, but it is not usual in this population that three out or nine eggs fail to hatch (Rodríguez et al, 2016). Great tits lay many eggs in relation to the brood patch size of the female, so she had to continuously change the relative position of the eggs in the nest so that all of them receive enough heat (Diez-Méndez et al, 2020).…”

“…Since 1986, we regularly monitor a great tit population breeding in nest boxes in orange (Citrus aurantium) plantations in Sagunto (eastern Spain, 39º 42' N, 0º 15' W, 30 m a.s.l.) (Álvarez and Barba, 2014;Rodríguez et al, 2016). Each year, we check the nest boxes weekly during the breeding season (from March to July) and we record the presence of nests, their progress and their contents.…”

“…Each year, we check the nest boxes weekly during the breeding season (from March to July) and we record the presence of nests, their progress and their contents. For each great tit clutch, we record the laying date of the first egg, clutch size, and number of hatchlings and fledglings (Rodríguez et al, 2016). We capture the parents using door-traps at the nest boxes when the nestlings are 10 days old.…”

A higher incidence of moult–breeding overlap in great tits across time is linked to an increased frequency of second clutches: a possible effect of global warming?

“…The study was conducted in two wild great tit populations breeding in nestboxes in Spain One was located within an extensive orange Citrus aurantium monoculture near Sagunto (Valencia, eastern Spain; 39º 42' N, 0º 15' W, 30 m a.s.l. ), and data relevant for the present study are available between 1995 and 2019 (Álvarez and Barba, 2014;Rodríguez et al, 2016). The study area in Sagunto has changed over the years, from about 150 ha in the first years to about 450 ha in recent years, but the density of nestboxes has remained almost constant at about 1 nestbox per ha.…”