DOI: 10.5061/dryad.95x69p8t6
title: It is good to be average: Ecological correlates of breeding phenology in an Arctic seabird, Alle alle (Dovekie)

description: Recognising importance of deviation from a population mean in an
 animal's behavior is not only necessary to understand the evolution
 and stability of the whole system but also to predict the future of a
 population in an altering environment. Arctic seabirds are expected to
 exhibit high synchronization in timing of breeding at the population
 level, due to highly seasonal and harsh environmental conditions.
 Nevertheless, even in such a highly synchronized system, there are always
 some earlier and later breeders, and what causes this inter-pair variation
 remains an intriguing question. Using a set of eight years of data on the
 dovekie (Alle alle), a small Arctic seabird, we examined potential drivers
 of the observed distribution of breeding phenology. We found that dovekie
 pairs were quite repeatable in their phenology, and preserved their
 phenological status, with their chicks hatching consistently before,
 during, or after the population median date for hatching, despite that
 calendar position of the median shifted between years. This would suggest
 that the timing of breeding is associated with some pair characteristics,
 either via properties of the nest or/and some partners traits. However,
 breeding phenology of the pair was not dependent on nest location, neither
 pair bond duration nor morphological similarity of the partners.
 Importantly, timing of breeding was negatively associated with chick
 growth rate, indicating fitness consequences of phenology. Our simulation
 further suggests that chance of fledgling survival in the context of
 predation may be the highest for the chicks that hatched during the peak
 of hatching period. While our results suggest that the timing of the
 breeding is important for the reproductive outcome, further research is
 required to determine the drivers of the repeatability within the dovekie
 pairs.
description: Data were collected in the dovekie breeding colony in Hornsund
 (SW Spitsbergen, 77°00′ N, 15°33′ E). Collected data (eight study seasons)
 include: phenology of breeding pairs of known identity (hatching date) and
 growth rate of their chicks, pair characteristics (partners morphological
 similarity) and GPS coordinates focal pairs nest. To establish pairs
 phenology and chick growth rate focal nests were controlled every 2-4
 days. To establish partners characteristics, focal individuals molecularly
 sexed and measured. Coordinates of focal nests were taken with a manual
 GPS.
description: # It is good to be average: Ecological correlates of breeding phenology in
 an Arctic seabird, Alle alle (Dovekie)
 [https://doi.org/10.5061/dryad.95x69p8t6](https://doi.org/10.5061/dryad.95x69p8t6) The present data set combines eight years of data (2015-2022) on the dovekie phenology from a breeding colony in Hornsund (Spitsbergen). The data set includes hatching date, chick growth rate, characteristics of the breeding pairs (partners morphology) and GPS position of the nest of the focal pairs. The separate data files may be merged by the nest or pair identity column; season may also be considered if the two data to be merged are season-specific. ## Data description This data set consists of four files: **Data_PairSimilarity.csv** - data on morphologicical similarity of the dovekie breeding pairs in respect to their phenology index. Similarity index calculcated using wing length of the two partners (see the main paper for details on the index caclulation), the interpretation of the index is as follows: the higher value of the index the bigger partners similarity. Phenology index is a standardized deviation of hatching date of a breeding nest/pair in respect to the median hatching date in given year. Negative values indicate on hatching before median (e.g. - 2 means two days before median), 0 denotes hatching during the median and positive values indicate hatching after median (e.g. +2 means two days after median) (see the main paper for details on the index caclulation). * Hatch_day: Consecutive calendar year (counting from Jan 1st of given year) * Hatch_date: Date of hatching for given pair * Nest: Nest identity; the variable used for the nest location analysis only  * Pair_ID: Pair identity (often identical with Nest identity but sometimes different, when there was a partners change); the variable used for all the analyses except the analysis on nest location * Phenol_Index: Phenological index  * Similarity_index:Index of partners similarity in wing length **Data_PairAge.csv** - data on "marital" status of study pairs - *Pair status* column: old and newly formed pairs. Old pairs are those which partners were together in the previous season(s) ("Old" value in the column) ; New pair are those which partners are breeding together for the first time ("New" value in the column"). Empty cells in the Pair status column are for pairs which status could could not been established. All the other variables as in **Data_PairSimilarity.csv** file. **Data_Nest_Location.csv** - data on geographical coordinates (X- longitute, Y-latitute) of the nest of study pairs; the file to be merged with **Data_PairSimilarity.csv** and **Data_PairAge.csv** by *Nest* and *Pair_ID* columns to get phenological index and perform the spatial analysis on the phenological index. **Data_Chickgrowth.csv**- data on body mass of chicks of focal pairs in all the study years; the file to be merged with **Data_PairSimilarity.csv** or **Data_PairAge.csv** by Nest and Season columns to get phenological index and perform the analysis on the releationship between phenological index and chick growth rate. * Season- study year * Dt- Date of chick weighting * Nest- Nest identity of the chick * BodyMass - Body mass in grams (each chick measured multiple times during the season; based on that was calculated the slope of the chick growth rate, to be further used in the analyses). Word document presents summary and additional results for the associated paper (on Zenodo) R script provides a code for the simulation described in the associated paper. (on Zenodo) ## Sharing/Access information Contact corresponding author for any clarification: Katarzyna Wojczulanis-Jakubas, University of Gdańsk, [katarzyna.wojczulanis-jakubas@ug.edu.pl](mailto:katarzyna.wojczulanis-jakubas@ug.edu.pl)