Abstract
An increasing number of studies report coordinated chick provisioning by avian parents. Although the pattern of parental coordination varies across species, broad occurrence of this coordination suggests that it has an adaptive value: it may increase individual fitness via higher offspring survival, faster offspring growth rate and/or higher body reserves of the parents. However, to what extent the pattern of coordinated provisioning in a species represents a flexible response to current foraging conditions remains an open question. Here, we examined coordination of chick provisioning in the Little Auk (Alle alle), a planktivorous seabird species that breeds in the Arctic. Harsh environmental conditions impose bi-parental care on this species, and high variability within and across breeding seasons promotes flexibility in parental involvement to secure breeding success. During the chick rearing period, parents exhibit a dual-foraging strategy (i.e. alternating long foraging trips, serving to maintain the adults’ body reserves, with several short trips aimed to provision the chick). We examined coordination of parental provisioning across five breeding seasons varying in terms of environmental conditions and found that the parents indeed coordinate their provisioning, avoiding performing long trips simultaneously and thus enabling a more even distribution of feeding through time. We also examined chick body condition in relation to the level of parental coordination to test the potential adaptive value of coordination, but we found no significant relationship between these two parameters. We found high variability in the level of the coordination between pairs, and this variability was similar across all study seasons, which represented a wide range of experienced environmental conditions. Nevertheless, we found that the energy density of food loads delivered to chicks was associated with the level of parental coordination: when conditions were characterised by the delivery of higher-energy food loads, the level of coordination exhibited by the studied population was higher. These findings suggest that environmental conditions somehow affect parental coordination, but the range of the environmental variation could be still below a critical threshold of extreme conditions that would trigger more pronounced modifications of parental foraging patterns and coordination.
Highlights
Ecological conditions associated with food availability and predatory pressure are among the most important determinants of benefits and costs of parental care in birds and are thought to play an important role in the evolution of avian breeding systems (Silver et al, 1985; Martin, 1987; Arnold and Duvall, 2002; Fontaine and Martin, 2006; but see Olson et al, 2008; Remeš et al, 2015)
We found that the frequency of 10-min time-windows in which one pair member was on short trip (ST) while the other was on long trip (LT) was significantly greater than expected by chance according to the combined p-value from our Monte Carlo randomization tests (Z = 2.47, P = 0.007), indicating coordinated provisioning
Our results showed that Little Auk parents coordinate chick provisioning, adjusting the timing of ST and LT to those of the partner, thereby reducing the variation in the duration of interfeeding intervals
Summary
Ecological conditions associated with food availability and predatory pressure are among the most important determinants of benefits and costs of parental care in birds and are thought to play an important role in the evolution of avian breeding systems (Silver et al, 1985; Martin, 1987; Arnold and Duvall, 2002; Fontaine and Martin, 2006; but see Olson et al, 2008; Remeš et al, 2015). Patterns of parental coordination may vary across groups, species and even breeding stages (e.g., alternated vs intermittent incubation, alternated vs overlapped feeding patterns, etc.), but overall, coordination of efforts by both breeding partners may substantially increase their reproductive success (e.g., Davis, 1988; Raihani et al, 2010; Mariette and Griffith, 2015). This seems to be important in extreme ecological conditions. Coordination per se is relatively rarely examined, and studies examining the issue in the context of environmental constraints are even more scarce
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