Fitness benefits of alternated chick provisioning in cooperatively breeding carrion crows
Data files
Nov 19, 2023 version files 2.56 MB
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02_nests_merged.csv
444.53 KB
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clutch_1.xlsx
14.10 KB
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cv.xlsx
14.58 KB
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egg_size.xls
2.03 MB
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nestling_mass_1.xlsx
15.21 KB
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nestling_mass58.xlsx
15.25 KB
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nestling_survival_1.xlsx
12.93 KB
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post_fledging_survival.xlsx
15.15 KB
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README.md
3.16 KB
Abstract
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.
README: Fitness benefits of alternated chick provisioning in cooperatively breeding carrion crows
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 6th 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.
Methods
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 Corvus corone 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 k-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.