DOI: 10.5061/dryad.gb5mkkx35
title: Parental effort in warming young: A neglected component of life history strategies influenced by nest structure, brood size, body mass, and bi-parental care

description: Parental care behavior has strong fitness consequences and has been widely
 studied, but variation in the effort that species invest in warming young
 has been neglected. Here, we investigate the extent and possible causes of
 variation in brooding, or warming, effort among 90 species of altricial
 birds on four continents. We measured parental warming effort based on the
 percentage of time parents spent warming young for the first approximately
 6 h of each day over the entire nestling period of each species. Our
 measure of warming behaviour was based on 62,249.5 hours of video data
 over 10,770 video days while studying 33,777 nests. We calculated the
 initial magnitude of effort at the start of the nestling period and the
 rate that effort declined with the age of the nestlings. Higher initial
 magnitude and slower rates of decrease reflected higher effort. We found
 that brooding behavior varied extensively among species. Brooding effort
 was greater in species in which both parents shared the effort and those
 with greater energy reserves from larger body size, indicating effort is
 under energetic limitation. Brooding effort was substantially lower in
 enclosed-nesting species than in those using open-cup or cavity nests,
 consistent with predictions that enclosed nests better retain heat and
 reduce parental energy demand of warming. Effort was not simply related to
 thermal demands. Brooding effort increased with the number of young in the
 brood, opposite to expectations based on greater thermal inertia. Instead,
 the increase in warming effort with the number of young in the brood fits
 with life history predictions of those species being under selection for
 greater reproductive effort. Understanding how the costs and benefits of
 brooding effort interact with other evolved traits is essential for
 advancing parental investment and life history theory.
description: # Parental effort in warming young: A neglected component of life history
 strategies influenced by nest structure, brood size, body mass, and
 bi-parental care Dataset DOI: 10.5061/dryad.gb5mkkx35 We studied brooding
 (warming) behavior of parent birds of 90 species in four sites that ranged
 from South Temperate to Tropical to North Temperate: South Africa,
 Venezuela, Malaysia, and Arizona, USA. We examined the extent to which
 brooding behavior varied among species with respect to their nest
 structure, body mass, whether parents shared the behavior, and the number
 of young in the nest. We measured brooding behavior as the percentage of
 time spent on the nest warming young based on video recordings of parents
 throughout the entire period they had nestlings. We defined brooding
 behavior based on the magnitude of effort on the days that young hatched
 (i.e., start of the nestling period) and the slope (rate of change) of the
 decrease in brooding effort as nestlings grew and slowly developed their
 own ability to stay warm. File: Brooding-2.csv Variables: * site:
 Geographic site that species were studied * Phyloname: Latin scientific
 name of species * Nesttype: Nest structure type, with three options: open,
 enclosed or cavity * Magnitude: Percent of time spent brooding on hatch
 day for each species * slope: slope of the change in brooding effort with
 age of the offspring for each species * lmas: log10 of average adult mass
 (grams) * sharebrd: a dummy variable for no sharing (single-parent = 0) or
 sharing (both parents brood = 1) * NestBrdSz: mean brood size (number of
 young) for all nests of each species that had nestlings * VideoBrdSz: mean
 brood size (number of young) for all nests of each species that provided
 video data * FldgAge: mean age (days) that nestling fledged (left) the
 nest for each species