DOI: 10.5061/dryad.k98sf7mdx
title: Data from: Parental overproduction allows siblicidal bird to adjust brood size to climate-driven prey variation

description: Parental overproduction is hypothesized to hedge against uncertainty over
 food availability and stochastic death of offspring and to improve brood
 fitness. Understanding the evolution of overproduction requires
 quantifying its benefits to parents across a wide range of ecological
 conditions, which has rarely been done. Using a multiple hypotheses
 approach and 30 years of data, we evaluated the benefits of overproduction
 in the Blue-footed booby, a seabird that lays up to three eggs
 asynchronously, resulting in an aggressive brood hierarchy that
 facilitates the death of last-hatched chicks under low food abundance.
 Results support the resource-tracking hypothesis, as low prey abundance
 (estimated from sea surface temperature and chlorophyll-a concentration)
 led to rapid brood reduction. The insurance hypothesis was supported in
 broods of three, where last-hatched chicks’ survival increased after a
 sibling’s death. Conversely, in broods of two, results suggested that
 parents abandoned last-hatched chicks following first-hatched chicks’
 deaths. No direct evidence supported the facilitation hypothesis: the
 presence of a last-hatched chick during development did not enhance its
 sibling’s fitness in the short or long term. The value of last-hatched
 offspring to parents, as “extra” or “insurance” varied with indices of
 food abundance, brood size, and parental age. Ninety percent of
 overproduction benefits came from enabling parents to capitalize on
 favorable conditions by fledging additional offspring. Our study provides
 insight into the forces driving overproduction, explaining the
 adaptiveness of this apparently wasteful behavior and allowing us to
 better predict how overproduction’s benefits might be modified by ocean
 warming.
description: Every year, from 1989 to 2019, all nests in our study areas (2.6
 ha) were monitored over the breeding season from February through July.
 During nest inspections, every 3-6 days, breeders were identified and
 sexed based on vocal dimorphism (females grunt, males whistle), and chicks
 were marked with colored plastic bands after hatching, then measured (ulna
 length, mm), weighed and fitted with numbered steel bands at 70 days, when
 they fledged. 
description: # Parental overproduction allows siblicidal bird to adjust brood size to
 climate-driven prey variation Climatic and biological data used in the
 article. ## Description of the data and file structure The data is a zip
 file containing two Excel files File list: * DATA.xlsx * ReadME_DATA.xlsx
 ## File descriptions The DATA.xlsx file contains all the data utilized in
 the article. It comprises 16 sheets, each containing a distinct set of
 data utilized for the analyses. Correspondingly, the ReadME_DATA.xlsx file
 mirrors this structure, also consisting of 16 sheets. Each sheet in the
 ReadME_DATA.xlsx file offers a description of the columns' meanings
 within the associated dataset, along with a brief explanation of the data
 provided in that particular dataset. "NA" stands for
 non-available values when climatic and oceanic data were missing, or
 biological data could not be registered.