DOI: 10.5061/dryad.v15dv423w
title: Data from: Stay or go? Changing breeding conditions affect sexual difference in colony attendance strategies of Atlantic puffins Fratercula arctica

description: Male and female birds have different interests in reproductive investment,
 which in turn may increase negative effects of poorer breeding conditions
 caused by e.g., climate change or ecosystem regime shifts. Using a 33-year
 time series with resightings of Atlantic puffins Fratercula arctica
 individually colour-ringed as breeders in previous years, we show that the
 difference in colony attendance of male and female birds depends on the
 environmental conditions for raising young, proxied by the average
 duration of the chick period and size of the herring Clupea harengus fed
 to the chicks in the colony each year. The longer the chick period, and
 thus the birds’ overall investment in reproduction, the more was the sex
 ratio of adults sitting out on the colony surface biased in favour of
 males. An increase in herring size, indicating better feeding conditions
 for raising chicks, led to more observations of both sexes, and the
 increase was slightly more prominent for females than males. We discuss
 the results in relation to general life-history theory on sexual
 differences in trade-offs between individual investment in breeding and
 own survival. Our results suggest that females are increasingly more
 willing than males to invest in provisioning for the chick the longer the
 chick needs such care. This difference may also prove valuable as an
 indication of breeding conditions from only a short visit to a colony with
 colour-ringed birds of known sex.
description: The attendance data were collected by capture-mark-resighting
 (CMR) of adult breeding Atlantic puffins in a colony in North Norway. The
 birds were sexed by DNA (blood sample), and time since ringing was used as
 a proxy for their age. Mean dates of chick hatching and chick death or
 nest departure were estimated from monitoring the content of on average
 103 (range 34-284) individually marked active nest-burrows in the same
 colony throughout the chick period. The length of their main prey, age 0
 herring, was calculated from identifying and measuring all fish sampled in
 on average 75 (range 0-266) food loads collected by mist-netting adults on
 their way to the nest. In years with no food sampled, herring size was
 estimated from its realtionship with ICES recruitment indices for the
 Norwegian spring-spawning herring stock 2 years later. 
description: # Changing breeding conditions affect sexual difference in colony
 attendance of Atlantic puffins Fratercula arctica
 [https://doi.org/10.5061/dryad.v15dv423w](https://doi.org/10.5061/dryad.v15dv423w) ## Description of the data and file structure The following parameter coding was used for the data analysis in Anker-Nilssen et al. "Stay or go? Changing breeding conditions affect sexual difference in colony attendance strategies of Atlantic puffins *Fratercula arctica*". The coding is also repeated on top of the accompanying data file, which is in simple text format with columns separated by semicolons. Code: coded colour ring of individual puffin Year: year of observations Hatching_ref: Defines observation period - before or after hatching Obs: Number of observations Effort_hours: number of hours spent observing per year and period (Hatching_ref) Sex: male / female Age: Years since first ringed Date_laying: average laying date for each year Date_hatching: average hatching date for each year Chick_period: average length of chick period (days) for each year Herring_size: estimated average herring size (length in mm's) for each year ## Code/Software All analyses were made in R. The scripts used are presented in the accompanying .R file