Using an Electronic Monitoring System to Link Offspring Provisioning and Foraging Behavior of a Wild Passerine

Abstract

Although the costs of parental care are at the foundations of optimal-parental-investment theory, our understanding ofthe nature of the underlying costs is limited by the difficulty of measuring variation in foraging effort. We simultaneously measured parental provisioning and foraging behavior in a free-living population of Zebra Finches (Taeniopygia guttata) using an electronic monitoring system. We fitted 145 adults with a passive transponder tag and remotely recorded their visits to nest boxes and feeders continuously over a 2-month period. After validating the accuracy of this monitoring system, we studied how provisioning and foraging activities varied through time (day and breeding cycle) and influenced the benefits (food received by the offspring) and costs (interclutch interval) of parental care. The provisioning rates of wild Zebra Finches were surprisingly low, with an average of only one visit per hour throughout the day. This was significantly lower than those reported for this model species in captivity and for most other passerines in the wild. Nest visitation rate only partially explained the amount of food received by the young, with parental foraging activity, including the minimum distance covered on foraging trips, being better predictors. Parents that sustained higher foraging activity and covered more distance during the first breeding attempt took longer to renest. These results demonstrate that in some species matching foraging activity with offspring provisioning may provide a better estimate ofthe true investment that individuals commit to a reproductive attempt. Uso de un Sistema de Monitoreo Electrónico para Conectar el Aprovisionamiento de las Crías y el Comportamiento de Forrajeo en un Ave Paserina SilvestreRESUMEN.-Aunque los costos del cuidado parental hacen parte de la base de la teoría sobre inversión parental óptima, nuestro conocimiento sobre los costos subyacentes está limitado por la dificultad de medir la variación en el esfuerzo de forrajeo. En este estudio medimos simultáneamente el aprovisionamiento de las crias y el comportamiento de forrajeo en una población de vida libre de Taeniopygia guttata empleando un sistema electrónico de monitoreo. Ajustamos transponedores pasivos en 145 adultos y registramos sus visitas a cajas de anidación y comederos de forma continua a lo largo de dos meses. Después de validar la exactitud de este sistema de monitoreo, estudiamos cómo variaban las actividades de aprovisionamiento y alimentación en el tiempo (en el dia y en el ciclo anual) y cómo influenciaban los beneficios (alimento recibido por las crías) y los costos (intervalo entre posturas) del cuidado parental. Las tasas de aprovisionamiento fueron sorpresivamente bajas, con un promedio de sólo una visita por hora a lo largo del día. Esto fue significativamente más bajo que lo que se había documentado para esta especie modelo en cautiverio y para la mayoría de otras aves paserinas en el campo. La tasa de visitas a los nidos sólo explicó parcialmente la cantidad de alimento recibida p...

Daily foraging patterns in free-living birds: exploring the predation–starvation trade-off

“…Crepuscular and nocturnal predators such as owls often begin foraging before sunset, and this potential addition to the predator community could increase the risk of predation such that late-day foraging is no longer offset by the fitness gains of continued feeding. Previous research on wild zebra finches (Taeniopygia guttata) during the breeding season [34] and dark-eyed juncos (Junco hyemalis) during winter [35] also demonstrated an early termination to feeding, with birds relinquishing more than an hour of potential feeding time in the evening. Predation pressure is probably not constant over the course of a day [36], and a consistent late-day peak in predator activity (e.g.…”

Individual variation in workload during parental care: can we detect a physiological signature of quality or cost of reproduction?

“…Nevertheless, the simplest and most commonly used measure of parental effort continues to be the number of visits/unit time to the nest or per chick (correcting for brood size) as discussed above. It is generally difficult to collect large amounts of data for many individuals on these other components of provisioning effort, but this is becoming easier with developments in nest cameras (García-Navas and Sanz 2010; Stodola et al 2010), RFID tags (Mariette et al 2011), automated radio-tracking systems that can cover relatively large areas of habitat (Mitchell et al 2012;Ryder et al 2012), or accelerometers Spivey and Bishop 2013). Thus, the goal should be to take a multivariate approach to obtain an integrated measurement of individual variation in parental workload coupled with physiological analysis of these same individuals.…”

“…2a) and chick mass at fledging. Many other studies have reported that chick mass and/or brood size at fledging are independent of interindividual variation in adult provisioning rate (Dawson and Bortolotti 2003;Garcia-Navas et al 2012;Mariette et al 2011;Ringsby et al 2009;Schwagmeyer and Mock 2008b).…”

Personality in captivity: More exploratory males reproduce better in an aviary population

“…Each of the feeders was essentially a finch cage containing a 50 × 30 cm seed tray with plentiful commercial finch mix that could only be entered through an 11 × 11 cm circular opening. Around this opening was a powered antenna (11 cm diameter) connected to a PIT-tag detection system (LID-665 decoder; Trovan, UK) that automatically recorded the unique identification of any tagged bird going through the entrance along with date and time information (Mariette et al, 2011). During each trial the batteries on the decoders were replaced between 2 and 3 pm every day, and the data from the decoders downloaded.…”

“…Before being introduced into the breeding aviary (8 × 10 × 2 m), a small blood sample (<30 l) was taken from the brachial vein and stored in 95% ethanol. The previously sexually-segregated adults were simultaneously released into the aviary containing 34 nest boxes, each fitted with a singlecoil antenna (5 cm diameter) connected to a PIT-tag detection system (LID-665 decoder; Trovan, UK) fixed inside the nest box around the entrance hole (to record bird identification and time and date (Mariette et al, 2011)). The contents of the nest boxes were inspected every 5-10 days between 10 am and 3 pm to count the number of eggs and nestlings.…”