Feather nitrogen and carbon stable isotope (d15N and d13C) values for Golden-crowned Sparrows
Data files
Jun 16, 2025 version files 9.87 KB
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GCSP_isotope_data.csv
7.26 KB
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README.md
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Abstract
Differential foraging by sex can have important implications for understanding the ecology of a species. This can be especially difficult to study through observations alone in sexually monomorphic species, such as the Golden-crowned Sparrow (Zonotrichia atricapilla), and for species in remote areas. We used nitrogen and carbon stable isotope analysis to determine the relative trophic position between the sexes for 73 individuals for this migrant songbird with little known diet information while breeding in remote locations of Alaska and northwestern Canada.
We found that females had significantly higher values of feather δ15N (mean 5.44 ‰; mean for males 4.54 ‰) after accounting for year and feather collection location, and in a subset of GPS-tagged birds with known breeding locations, after accounting for year, breeding latitude, elevation, or distance to shoreline. We infer that females may be foraging more items from a higher trophic level than males on breeding grounds, which may reflect a physiological need to replace lost nutrients from nesting.
Dataset DOI: 10.5061/dryad.0000000fz
Description of the data and file structure
The data includes stable isotope values of carbon and nitrogen (d15N and d13C) collected from feathers (outer rectrices) of Golden-crowned Sparrows. Where known, age, wing chord length (mm), and mass (g) are provided, as well as the wintering location where feathers were collected. Sex is given, as well as how sex was determined (i.e., genetically or using wing-chord lengths).
Files and variables
File: GCSP_isotope_data.csv
Variables
- Band_no: Federal band number
- feath_coll_loc: Where the feathers were collected. This includes Parksville on Vancouver Island, British Columbia, Canada (PABC), the University of California, Davis campus, Yolo County (UCD), Hagmaier Ranch in Olema Valley, Point Reyes National Seashore, Marin County (HAGM), Malibu, Los Angeles County within the Santa Monica Mountains National Recreation Area (ZUMA), and in Newcastle, California, in Placer County (NEWC)
- Feath_coll_date: The date the feathers were collected in MM/DD/YYYY format.
- know_orig: Whether or not the origin is known for where feathers were grown, assuming feathers were grown at breeding grounds during normal prebasic molt. This is for a subset of birds that had been tracked with GPS.
- age: Age of birds. AHY = After hatch year; ASY = After second year; SY = Second year.
- wing_mm: Wing chord length of birds in mm. NA = measurement not available.
- mass_g: Body mass of birds in grams
- Sex: Male or female
- sample_weight_mg: Weight of the sample for stable isotope analysis, in mg
- N2_Amp: The amplitude of the sample peak in mV of N2
- perc_N: The elemental percentage of nitrogen based on weight
- d15N: The corrected isotope delta value for 15N measured against a primary reference scale (atmospheric air)
- CO2_Amp: The amplitude of the sample peak in mV of of CO2
- perc_C: The elemental percentage of carbon based on weight
- d13C: The corrected isotope delta value for 13C measured against a primary reference scale (Vienna Pee Dee Belemnite)
- batch_paper: The batch the samples were run in at the lab where the number refers to the appendix of the associated manuscript and gives values for standards that were run during processing
- how.sexed: If genetic, feathers were processed at a lab to determine sex. If assigned, sex was determined based on wing chord length, following a process described in the associated manuscript
We collected feathers in the months of October-March from individuals at five study sites across the Golden-crowned Sparrow wintering range (western regions of Canada and the United States) from 2019-2021. We collected 8-10 contour feathers for genetic sexing and two outer tail feathers (rectrices) for stable isotope analysis. Due to funding limitations, we were only able to genetically determine sex for a subset of the birds with stable isotope information, leaving some birds with stable isotope values but unknown sex. We used wing chord values to sex an additional 13 birds (see paper for additional details), for a total of 73 individuals with stable isotope values and an assigned sex. Feathers were processed at the Cornell Isotope Laboratory at Cornell University, Ithaca, NY, USA.