DOI: 10.5061/dryad.wpzgmsbv1
title: Fitness benefits of alternated chick provisioning in cooperatively breeding carrion crows

description: In most bird species, parents raise offspring cooperatively. In some
 cases, this cooperation extends to helpers-at-the-nest who assist the
 breeders with a range of tasks. While cooperative food provisioning might
 merely arise incidentally, as a result of the efforts of carers that act
 independently from each other, recent studies suggest that birds may
 coordinate by taking turns in visiting the nest. However, evidence that
 such coordination emerges because individuals actively respond to each
 other’s behaviour is controversial, and the potential benefits of carers’
 alternation remain unknown. We addressed this knowledge gap by analysing a
 multi-year dataset for cooperatively breeding carrion crows, Corvus
 corone, comprising 8,693 nest visits across 50 groups. Our results reveal
 that turn taking does occur in this species and that all group members,
 regardless of their sex and social role (breeder/helper), tend to
 alternate at the nest with other carers rather than to make repeat visits.
 Importantly, we found that the body mass of nestlings increased
 significantly with the degree of carers’ alternation, possibly because
 well-coordinated groups provided food at more regular intervals. Using
 earlier monitoring data, the observed increase in body mass is predicted
 to substantially boost post-fledging survival rates. Our analyses
 demonstrate that alternation in nestling provisioning has measurable
 fitness benefits in this study system. This raises the possibility that
 cooperatively breeding carrion crows, as well as other bird species with
 similarly coordinated brood provisioning, exhibit specialized behavioural
 strategies that enable effective alternation.
description: During the breeding seasons of
 1999–2000, 2003–2007, 2015, 2018 and 2019, we monitored a total of 50
 nests of cooperatively breeding carrion crows <em>Corvus
 corone</em> with camouflaged small video-cameras. First, we
 investigated if crow carers took turns when visiting the nest to feed the
 brood and if the tendency to alternate varied among types of carers
 (breeders/helper). To do so, we applied the
 <em>k</em>-categories runs tests, a randomization test that
 accounts for the “refractory time” between successive visits of the same
 carer and Continuous Time Random Models. Second, we investigate if better
 nest visit alternation among carers was linked with higher reproductive
 output (proportion of chicks fledged) and/or higher nestling quality,
 using Generalized Lineal Mixed Models. We also performed additional
 analyses to elucidate whether the correlations found were causal. For
 details, see Trapote et al. Fitness benefits of alternated chick
 provisioning in cooperatively breeding carrion
 crows.
description: # Fitness benefits of alternated chick provisioning in cooperatively
 breeding carrion crows
 [https://doi.org/10.5061/dryad.wpzgmsbv1](https://doi.org/10.5061/dryad.wpzgmsbv1) **ANALYSIS OF ALTERNATION**   *Data file:* 02\_nests\_merged.cvs : it contains all data used in the analysis of coordination   *Column headers* NestID: Nest Identity Year Individual: individual identity Sex: M = male, F = female Role: Social status (Breeder/Helper) Sys\_ini: sys time at the beginning of the nest visit Sys\_end: sys time at the endo of the nest visit   R scripts: -        01\_k-category-test.R: k-category run tests -        02\_CTMM\_fit.R: Continuous Time Marcov models -        03\_randomization-test.R: randomization of inter-visit intervals (IVIs) -        04\_IVIS-wwtests.R: Wald Wolfowiz run test of randomness of long/short inter-visit intervals -        fit-markov.R: set of functions to fit nest visit data to Markov models -        randomization\_functions.R: set of fucntions to randomize inter-visit intervals for coordination analyses -        ww\_test.R: function that performs the Wald-Wolfowitz run test     **FITNESS CONSEQUENCES OF ALTERNATION**   *Data files (see the R script for details on the models):* -        nestling\_survival1.xlsx : it contains data on the number of eggs in the clutch that produced/did not produce a fledging. -        nestling\_mass1.xlsx : it contains data on body mass and condition (mass/tarsus length).   -        nestling\_mass58.xlsx : Like the file above, but including an outlier. -        post\_fledging\_survival.xlsx : it contains data on crow survival three months after fledging. -        egg-size.xls : it contains data on egg volumes -        clutch\_1.xlx : it contains data on clutch size -        cv.xlsx : it contains data on the coefficients of variation of inter-nest visits intervals.     *Metadata: Column headers*   year terr (or territory) = Territory ID (either a number or a letter) group (or group\_size) = group size julian (or laying date) = julian date of first egg laid (days) fledg = number of eggs that produced a fledging  dead = number of eggs that did not produced a nestling alternation = proportion of alternated visits at the nest feed\_rate = hourly frequency of brood feeding (all carers) cond = nestling body condition (mass(gm) /tarsus length (mm)) mass = nestling body mass (gm) age = length of the 6<sup>th </sup>primary feather (cm) (proxy of age) sex = M = male, F = female brood = brood size clutch (or clutch\_size) = clutch size fate = survival at three months after fledging (1 = alive; 0= dead) brood ID = brood identity vt = egg volume (cm3) ind = individual ID cv = coefficient of variation of inter-nests visits intervals feed\_frec\_event= visit rate (with feed) per chick (nest visits per hour)   *R script:*   FITNESS\_BENEFITS.R : it includes analyses on proportion of nestling survived, nestling body mass and condition, post-fledging survival, egg and clutch size, total brood feeding rate and coefficient of variation of inter-visit intervals.