Analysis of the optimal duration of behavioral observations based on an automated continuous monitoring system in tree swallows (Tachycineta bicolor): Is one hour good enough?

Studies of animal behavior often rely on human observation, which introduces a number of limitations on sampling. Recent developments in automated logging of behaviors make it possible to circumvent some of these problems. Once verified for efficacy and accuracy, these automated systems can be used to determine optimal sampling regimes for behavioral studies. Here, we used a radio-frequency identification (RFID) system to quantify parental effort in a bi-parental songbird species: the tree swallow (Tachycineta bicolor). We found that the accuracy of the RFIDmonitoring systemwas similar to that of video-recorded behavioral observations for quantifying parental visits. Using RFID monitoring, we also quantified the optimum duration of sampling periods for male and female parental effort by looking at the relationship between nest visit rates estimated from sampling periods with different durations and the total visit numbers for the day. The optimum sampling duration (the shortest observation time that explained the most variation in total daily visits per unit time) was 1h for both sexes. These results show that RFID and other automated technologies can be used to quantify behavior when human observation is constrained, and the information fromthese monitoring technologies can be useful for evaluating the efficacy of human observation methods

The cumulative number of parental visits in tree swallow nests in (A) Canada and (B) North-Carolina.

<p>In both (A) and (B), each panel corresponds to one nest (the nest identifier is printed above each panel), with the blue line representing the male and the red line the female parent.</p

Summary of published results testing different sampling regimes.

<p>Summary of published results testing different sampling regimes.</p

Proportion of variance explained (R²) and its 95% confidence interval generated by bootstrapping, statistical significance (p-values), and the sample size (N) of the relationship between 1h-samples and the total daily visit rate based on the time of onset of the 1h-sample for female and male tree swallows.

<p>Proportion of variance explained (R²) and its 95% confidence interval generated by bootstrapping, statistical significance (p-values), and the sample size (N) of the relationship between 1h-samples and the total daily visit rate based on the time of onset of the 1h-sample for female and male tree swallows.</p

Visit rate (the number of feeding visits/h) of female and male tree swallows inferred from 1h-behavioral observations (y-axis) and RFID readings (x-axis).

<p>Open circles denote influential data points that have disproportionate effect on the relationship as measured by the ‘influence.measures’ function in R. Note that the statistical analyses provided in the main text were carried out including these data points, and therefore provide a conservative estimate of these relationships.</p

Optimal durations of observation periods for female and male tree swallows.

<p>The solid lines show the best fit curve to the data (a three parameter Michaelis-Menten model) for the relation between R² and observation period duration (15 minutes—4 hours). The dashed lines show three alternative model fits (Gompertz, Asymptotic regression and General Additive Model). Red and blue dots indicate the optimal sampling effort for females and males respectively, that maximizes R² and minimizes the duration of observation (indicated by the dashed arrows).</p

Geolocator tagging links distributions in the non-breeding season to population genetic structure in a sentinel North Pacific seabird.

We tested the hypothesis that segregation in wintering areas is associated with population differentiation in a sentinel North Pacific seabird, the rhinoceros auklet (Cerorhinca monocerata). We collected tissue samples for genetic analyses on five breeding colonies in the western Pacific Ocean (Japan) and on 13 colonies in the eastern Pacific Ocean (California to Alaska), and deployed light-level geolocator tags on 12 eastern Pacific colonies to delineate wintering areas. Geolocator tags were deployed previously on one colony in Japan. There was strong genetic differentiation between populations in the eastern vs. western Pacific Ocean, likely due to two factors. First, glaciation over the North Pacific in the late Pleistocene might have forced a southward range shift that historically isolated the eastern and western populations. And second, deep-ocean habitat along the northern continental shelf appears to act as a barrier to movement; abundant on both sides of the North Pacific, the rhinoceros auklet is virtually absent as a breeder in the Aleutian Islands and Bering Sea, and no tagged birds crossed the North Pacific in the non-breeding season. While genetic differentiation was strongest between the eastern vs. western Pacific, there was also extensive differentiation within both regional groups. In pairwise comparisons among the eastern Pacific colonies, the standardized measure of genetic differentiation (FꞌST) was negatively correlated with the extent of spatial overlap in wintering areas. That result supports the hypothesis that segregation in the non-breeding season is linked to genetic structure. Philopatry and a neritic foraging habit probably also contribute to the structuring. Widely distributed, vulnerable to anthropogenic stressors, and exhibiting extensive genetic structure, the rhinoceros auklet is fully indicative of the scope of the conservation challenges posed by seabirds