Delayed dispersal in splendid fairywrens
Data files
Jun 05, 2024 version files 24.87 KB
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README.md
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SPFW_natural_dispersal_outcomes-DRYAD.csv
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SPFW_removal_exp-DRYAD.csv
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Abstract
Delayed dispersal is a critical first step in the formation of both cooperative breeding and family-living groups. However, disentangling the multiple, potentially co-occurring factors that influence the dispersal of young individuals is often difficult and can require multiple data sources. We combine data from a long-term mark-recapture study and field experiments to address the patterns, fitness consequences, and proximate causes of delayed dispersal in the splendid fairywren (Malurus splendens melanotus). This species is a cooperative breeder, with males remaining as helpers more often for more years and settling closer to their natal territories than females. We found that birds who were helpers in one or more years had greater first-year nest success, and the number of years spent helping had a positive impact on survival. By experimentally producing breeding vacancies for young males, we tested if male-biased sex ratio and breeding opportunities constrained dispersal in this system. Only half of the vacancies created were filled, and dispersal took, on average, approximately three days. These findings illustrate that ecological constraints, benefits-of-philopatry, and life history benefits may all be acting within the same system to shape dispersal patterns.
README: Delayed dispersal in Splendid Fairywrens
https://doi.org/10.5061/dryad.rjdfn2zm8
Here are found two datasets describing delayed dispersal behavior in a population of Splendid Fairywrens (Malurus splendens melanotus). Below, we detail the contents of each file individually. Included is R code for conducting the analyses described in the manuscript.
Description of the data and file structure
File No. 1: "SPFW natural dispersal outcomes-DRYAD.csv"
1. ID -- unique identifier for each individual
2. sex -- binary variable "F" = female, "M" = male
3. hatch_year -- year the bird was born
4. natal_group -- group that they were hatched out from. If the bird remained a helper, this will likely be the same as the first_year_group (etc.) but may not always be, as sometimes group names shifted. Status is determined based on group composition. A prefix of "VWG" indicates purple-backed fairywren group, a prefix of "SWG" indicates splendid fairywren group.
5. first_year_status -- three options: "helper" = a subordinate member of that sex in the group; "breeder" = the dominant, or breeding, member of that sex in the group, or "unknown" = where the bird was resighted and the location was known but their social status was unknown
6. first_year_group -- ID for the group the bird was in its first year
7. first_year_location -- Is the first year territory location relative to its natal location. Is one of the following three categories: natal = in the same location as its natal terrritory (true even if territory center shifted slightly as long as it is in the same general area and the social father wasn't in the same natal location); ajacent = is in a territory that shares a border with it's natal territory (common when social father is still alive in natal territory, or a sibling has inherited the natal territory); distant = one or more territories separate the first year territory from the natal territory.
8. first_year_location_bin --combines the categories above "natal" and "ajacent" into one group, still called "natal". This was done because birds who settle in a territory adjacent to their natal territory are not truely making a disperal movement. This is the primary metric used in the manuscrip.
9. number_years_helping -- number of years which the individual was observed helping prior to becoming a breeder for the first time. Is NA if unsure. Is listed as a whole number if the bird began the season as a helper but transitioned to a breeder mid-way through due to the death of a another breeder (e.g., if the bird was a helper in its first year, but half way through became a breeder is still listed as 1 yr and not a decimal). In a few cases a bird became a breeder then transitioned back to a helper. If so, this number does not include any additional helping years, only the number of years prior to first breeding attempt.
10. became_breeder -- binary variable, Y = yes became breeder, N = no did not become breeder (during the period of resigning), or is NA if unknown
11. year_first_breeding -- year that the bird was first observed breeding, is NA if was never seen breeding or if the status became unknown
12. age_first_breeding -- age that the bird was when first a breeder. Is the breeding year - hatching year, or is NA if they did not become a breeder or the status is unknown.
13. first_nest_to_6DO -- binary, if 0 they did not get a nest to 6DO in their
14. first_breeding_group -- ID for the group the bird was in its first year as a breeder
15. first_breeding_location -- Is the bird's first breeding territory location relative to its natal location. Is one of the following three categories: natal = in the same location as its natal terrritory (true even if territory center shifted slightly as long as it is in the same general area and the social father wasn't in the same natal location); ajacent = is in a territory that shares a border with it's natal territory (common when social father is still alive in natal territory, or a sibling has inherited the natal territory); distant = one or more territories separate the first year territory from the natal territory.
16. first_breeding_loc_bin -- combines the categories above "natal" and "ajacent" into one group, still called "natal". This was done because birds who settle in a territory adjacent to their natal territory are not truely making a disperal movement. This is the primary metric used in the manuscrip.
17. years_present -- number of years a bird was present in the population; is NA if the status of the bird was unknown (true if was still alive at the end of this dataset, and we don't have an end age).
18. Notes -- a note column. Explains why a nest was not included for some birds, why a territory name might not match, or why fate might be unknown for some birds.
Missing data code: NA
File No. 2: "SPFW removal exp-DRYAD.csv"
This file contains the setup and outcomes of experimental breeding vacancy production for male splendid fairywren helpers. Details of the experimental protocol can be found within the manuscript, but note removed birds were released alive in suitable habitat. Below are column by column descriptions of each variable.
1. Experiment_no -- the order in which the experiments occured, values are 1-14
2. Initial_group_size -- the original size of the focal group before removals were conducted. A value of 2 indicates the group consisted of only a breeding pair (and thus only 1 bird, the breeding male, was removed). A value of 3 indicates a breeding pair with a male helper, one case only. In that case 2 birds (the breeding male and the helper male) were removed from the social group.
3. No_adjacent_groups_with_potential_dispersers -- numeric, the number of groups adjacent to the focal group which contained one or more helper males, individuals which could become dispersers.
4. Total_no_potential_dispersers -- numeric, the number of helper males in adjacent territories, that is the number of nearby individuals who could become dispersers.
5. Day -- day of the month on which the experiment was conducted
6. Month -- month in which the experiment was conducted (10 -- October, 11 -- November)
7. Year -- the year in which the experiment was conducted, either 2017 or 2018
8. Time_of_removal -- time when the initial removals occured
9. Did_dispersal_occur -- indicates whether a dispersal did (Yes) or did not occur (No)
10. Dispersers_aware_of_vacancy -- indicates whether potential dispersers were seen visiting the focal territory. In all cases this value is "Yes"
11. Outcome -- as not all experiments resulted in a dispersal (see 10), this column describes the different outcomes. Three values are possible: 1) "Dispersal" indicates a male dispersed into the breeding vacancy, 2) "Merge" indicates that a nearby territory merged with the focal group, resulting in the lone breeding female becoming a helper, and 3) "Solitary" indicates that either the lone breeding female remained alone or disappeared after a few days alone.
12. Time_to_dispersal_hours -- numeric, number of hours before a dispersal occured. Values of NA are provided for those experiments that did not result in a dispersal
13. Status_of_disperser -- location status of the dispersing male. Three values are possible: 1) "Neighbor" indicates the male came from a territory adjacent to the focal territory, 2) "Unknown" indicates we were unsure of the origin of the dispersing male, and 3) "NA" is provided if a dispersal did not occur
14. Merge_group_status -- location status of the merging territory owner if a merge between the focal territory and another occured. Is either "Neighbor", an adjacent territory to the focal territory, or "NA" in the cases where a merge did not occur.
Missing data code: NA
Code/Software
Analyses described in the manuscript were conducted in R (R Core Team 2024). Attached is an Rmd file with the code used to conduct analyses, entitled "SPFW data analysis Dryad.rmd".
Methods
This data comes from a long-term study of color-banded splendid fairywrens (Malurus splendens melanotus) that has been conducted at Brookfield Conservation Park since 1992, and contains both an observational study of natural behavior and an experimental study.
Natural dispersal behavior
We assessed the natural dispersal behavior of splendid fairywrens hatched between 2004 and 2018, the longest uninterrupted stretch of monitoring in this population. Observations on the dispersal behavior of these individuals were conducted between 2005 and 2020. Only young banded as nestlings or as fledglings that were resighted in their first full breeding season (an age status which we refer to as first-year) were included. We categorized the first-year social status of each known-age offspring as either breeders or helpers. For each individual, we also categorized the first-year territory location. First-year territories could either be 1) near—in the same territory that they were hatched in or in an immediately adjacent territory, a proxy for natal philopatry or 2) distant—a territory that had one or more territories in between it and their natal territory. For females, the proportion of young who remain near their natal territory is likely an overestimate of the true values within the population as many females disperse out of the study population, and their final breeding location is never known (Rowley and Russell 1997; Pruett-Jones et al. 2010).
For a subset of individuals that persisted in the population beyond their first year, we also collected the following data: the number of years (if any) spent as a helper, the age at which they first bred (if applicable), the location of first breeding (near or distant, if applicable), their first-breeding-year success, and the number of years present in the population. First-breeding-year success was the success of a nest in the bird’s first season as a dominant individual and was determined by whether the bird’s social group produced a nest that progressed to nestlings of 6-8 days old, the age at which we banded nestlings.
Experimental studies of male dispersal behavior
Breeding opportunities were created for 14 male splendid fairy-wrens (eight in 2017, six in 2018). For 13 of these removals, a single male was removed (group size of the focal territory of two), and for one experiment, two males were removed (a dominant male and a subordinate male). For each experimental group, we monitored the remaining female and the territory site for two hours immediately following the removal of the breeding male(s) and again in the afternoon on the day of removal. If no dispersal occurred on the day of the removal, we continued to monitor the territory twice each day until the vacancy was filled or two weeks had passed. After two weeks, we continued to check on the experimental territory every other day. There were three possible outcomes of each experiment: 1) a dispersal occurred, 2) a territory merger occurred in which an adjacent social group expanded its territory to include the focal territory and the remaining female, or 3) the remaining breeding female held the territory alone or left the area (collectively referred to as ‘solitary’). For each experiment, we recorded the outcome and the latency to dispersal if a dispersal occurred. Latency to dispersal was documented as the number of hours till a dispersal was observed, rounded to the nearest half-day after the first day following removal. We also documented whether males from surrounding territories visited the experimental territory to establish if neighboring birds were aware of the breeding vacancy. No males who ultimately dispersed into breeding vacancies were included in the natural history data.