Data from: Food supplementing peregrine falcon (Falco peregrinus tundrius) nests increases reproductive success without changes in parental mean provisioning rate
Data files
Aug 30, 2024 version files 1.71 MB
Abstract
Parents are expected to exhibit intermediate levels of investment in parental care that reflect the trade-off between current versus future reproduction. Providing parents with supplemental food may allow for increased care to the current brood (additive model), re-allocation of parental effort to other behaviours such as self-maintenance (substitution model) or may provide parents with a buffer against provisioning shortfalls (insurance model). We investigated the impact of parental food supplementation on provisioning behaviour and breeding success in Arctic-breeding peregrine falcons (Falco peregrinus tundrius) over five successive breeding seasons (2013-2017). We found that supplemental feeding had no impact on mean provisioning rates, yet resulted in increased nestling survival probability, increased nestling body mass, and decreased variance in nestling body mass and provisioning rates. These results are consistent with parents adopting a hybrid of the additive and substitution models. We suggest that food supplementation enables increased investment in other forms of parental care (e.g., nest defence, brooding) without altering mean provisioning rates. The lack of observed effects on mean provisioning rates, coupled with increased survival and body mass of offspring, suggests a potential reallocation of parental effort. The findings contribute to understanding the responses of peregrine falcons to food supplementation, highlighting the need for future studies to explore broader environmental contexts and potential long-term effects on parental survival and future reproduction.
README: Food supplementing Peregrine falcon (Falco peregrinus tundrius) nests increases reproductive success without changes in parental provisioning rate
Overview of files and their contents:
Code was written and analyses were completed in R (version 4.2.0). The complete R code needed to replicate the analysis in this study is provided, as well as the data files used. This is provided as 1 R studio file (.R) and three .csv files.
Descriptions of each file are provided below.
1. Final_Code_Supplementation.R
R file containing an anonymised version of the complete code (including packages) used for all analyses in this study.
Annotations are provided throughout the R file to ensure clarity about the steps taken. Code is grouped into titled sections indicating what was completed in that section (e.g., ‘load packages’, ‘load data as CSV files’) for ease of readability.
2. Mass_Data.csv
A .csv file containing data collected for the study. Column details are as follows:
| Column Title | Description of Contents |
|---|---|
| site | Nest site number – repeated across years. The same nest site locations were often occupied across multiple study years. Nest site locations were therefore numbered for ease of reference. |
| colour | The colour identifying a specific nestling. Each nestling was colour marked on its legs using non-toxic markers to facilitate tracking the mass of individual nestlings. Nestlings were marked with blue, red, or green markers, and a maximum of one nestling per nest site was left unmarked (typically the last-hatched nestling). ‘Black’ indicates that the nestling was unmarked. |
| year | Study year (2013-2017) formatted as YYYY. |
| age (days) | Nestling age at time of mass measurement. Age was calculated using hatch date, (see ‘Nestling_Details_Data.csv’) |
| mass (grams) | Nestling mass at time of nest visit. Nestlings were weighed using an electronic scale during each nest visit, every 5 days. |
| yearsite | The combination of the ‘year’ and ‘site’ columns. This provides a reference to year-specific site locations i.e., pairs (the breeding pair occupying that site in that year). |
3. Nestling_Details_Data.csv
A .csv file containing data collected for the study. Column details are as follows:
| Column Title | Description of Contents |
|---|---|
| year | Study year (2013-2017) formatted as YYYY. |
| site | Nest site number – repeated across years. The same nest site locations were often occupied across multiple study years. Nest site locations were therefore numbered for ease of reference. |
| yearsite | The combination of the ‘year’ and ‘site’ columns. This provides a reference to year-specific site locations i.e., pairs (the breeding pair occupying that site in that year). |
| surv | Binary record of nestling survival to fledging. 1 indicates the nestling survived to fledging, 0 indicates the nestling died before fledging. If the nestling died, the age at death was recorded (‘age_at_death’ below). |
| hatch_date | The date on which the nestling hatched, based on a review of nest camera images. The date is formatted as DD/MM/YYYY. |
| treatment | Binary indicator of the experimental category of that nest. 1 indicates the nest was food-supplemented, and 0 indicates the nest was not food-supplemented (i.e., it was a control nest). |
| age_at_death (days) | If the nestling did not survive until fledging, the age at death was recorded. If the nestling survived until assumed fledging, this column records ‘NA’. |
| hatch_date_in_july | The day in July on which that nestling hatched i.e., DD format of hatch_date. All nestlings in this study hatched in July. |
| clutch_size | The number of eggs laid at that yearsite location. Recorded as an integer value. |
| nestling_sex | The sex of that nestling. ‘f’ indicates that the nestling was female, ‘m’ indicates that the nestling was male. Nestling sex was determined using band size at the last nest visit (date recorded as ‘band_date’ below), so if the nestling did not survive the sex could not be determined and was recorded as ‘NA’. In some instances, the nestling survived but could not be banded; in these instances, the nestling sex was recorded as ‘unk’. |
| band_date | The date on which that nestling was banded. The date format is DD/MM/YYYY. Only surviving nestlings were banded, so ‘NA’ is recorded in this column for nestlings that did not survive to fledge. |
| nestling_sex_in | Nestling sex as an integer value for use in statistical analysis. 1 indicates that the nestling was female, and -1 indicates that the nestling was male. NA indicates that the nestling did not survive to be banded, and so sex could not be determined. ‘unk’ indicates that the nestling survived but could not be banded so sex could not be determined. |
4. IVI_Data_Revised.csv
A .csv file containing data collected for the study. Column details are as follows:
| Column Title | Description of Contents |
|---|---|
| site | Nest site number – repeated across years. The same nest site locations were often occupied across multiple study years. Nest site locations were therefore numbered for ease of reference. |
| yearsite | The combination of the ‘year’ and ‘site’ columns. This provides a reference to year-specific site locations i.e., pairs (the breeding pair occupying that site in that year). |
| chicks | Brood size on the date of nest observation, based on camera trap images (see ‘date’ below). If the camera trap failed to record images (e.g., due to a dead battery) the brood size was recorded as ‘NA’. |
| hatch_date | The date on which the nestling hatched, based on a review of nest camera images. The date is formatted as DD/MM/YYYY. |
| julian | Julian date of the hatch date i.e., the numerical value of days since January 1st, 1900. This was calculated in Excel. |
| julian2 | The day in the year of the hatch date where January 1st is day 1. |
| date | Actual date of nest observation, based on camera trap images. The date is formatted as DD/MM/YYYY. |
| jdate | Julian date of (observation) date in days i.e., the numerical value of days since January 1st, 1900. This was calculated in Excel. |
| jdate2 | Day in the year of the nest observation where January 1st is day 1. |
| start_day | Nest observation day formatted as DD. |
| start_month | Nest observation month formatted as MM. |
| year | Study year (2013-2019) formatted as YYYY. |
| visit_type | Indicator whether or not visits could be scored. If a visit could be scored, it was recorded as ‘provisioning’ indicating a provisioning visit made to the nest. If the camera failed (e.g., due to a dead battery) the visit type was recorded as ‘fail’ as provisioning visits could not be scored during that time. |
| start | Start time of the provisioning visit to the nest, or camera failure (see visit_type above). Time was formatted as HH:MM:SS. |
| sex | Sex of the parent observed at the nest. ‘m’ indicates that the parent was male, ‘f’ indicates that the parent was female. Where the visit type was ‘fail’ then ‘NA’ was recorded in this column. When the parental sex could not be determined based on the nest camera image ‘unknown’ was recorded. |
| end_day | Day on which the provisioning visit or nest camera failure ended formatted as DD. |
| end_month | Month on which the provisioning visit or nest camera failure ended formatted as MM. |
| supplemented | Indicator of the experimental category of that nest. y indicates the nest was food-supplemented, and n indicates the nest was not food-supplemented (i.e., it was a control nest). |
Instructions for users:
All analyses were completed using the R statistical environment (version 4.2.0) and can be run using the R script provided (Final_Code_Supplementation.R). Package versions are provided in script annotations. The user will need to ensure the file path is corrected to the location of the provided .csv files on their computer when loading the data.
Methods
For full methodological details, please refer to the full manuscript. In brief:
Parents at 52 nest sites were provided with supplemental food (quail) every 5 days (weather permitting) across the 5 study years; 75 nests were included as controls and were visited at the same regularity but not food-supplemented. Nest cameras were placed at nests included in the study, and photos were processed after the field season to extract data used to calculate inter-visit intervals (IVIs). Nestlings were also weighed during regular nest visits and were banded during the final nest visit. Data was analysed using Bayesian mixed-effect models using the 'brms' package in the R statistical environment (version 4.2.0).