Diet, phenology, and body size shape nutrient release by songbirds
Data files
Jan 28, 2026 version files 35.70 KB
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README.md
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songbird_waste_elemental_measurements.csv
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songbird_waste_phosphorus_analyses.csv
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Abstract
Animals can dramatically alter ecosystem structure and function through the cycling and transport of nutrients in their waste. While birds are particularly capable of influencing nutrient cycles due to their high mobility, abundance, metabolism, and functional diversity, the factors shaping variation in nutrient release among birds remain poorly understood.
We examined how trophic position, phenology, and body size shape the release of carbon (C), nitrogen (N), and phosphorus (P) in the waste of a diverse assemblage of songbirds. We analyzed waste samples (reflecting excretion and egestion) from 151 individual songbirds (31 species) at a migratory stopover site during one spring and one fall season in upstate New York, USA.
Trophic position, represented by δ15N in waste, correlated positively with %N and negatively with C:P. Waste stoichiometry also differed between seasons with higher %N and lower C:N in spring compared to fall as birds shifted their diets from N-rich insects in spring to C-rich fruits and seeds in fall.
Birds in the fall exhibited increased fattiness, and body size had the strongest influence on C, N, and C:N release during this season, suggesting that fat accumulation for energy storage may shape nutrient excretion prior to migration. However, the effects of body mass and its interactions with season and trophic position were complex.
Ultimately, trophic position, phenology, and body mass together helped explain variation in nutrient release among songbirds. Future research may leverage this information to further explore how migratory songbirds influence stopover habitats and other ecosystems via contributions to nutrient cycling.
Dataset DOI: 10.5061/dryad.jq2bvq8q6
Description of the data and file structure
These datasets contain the data for analyses examining how nutrient release among songbirds varies by body mass, trophic position (as indicated by δ15N), and season (fall vs. spring). Data collection took place in September 2021 (fall) and May 2022 (spring) at the Braddock Bay Bird Observatory for a total of 151 songbirds from 31 species, 18 genera, and 11 families. Each bird was banded following normal banding operations by the Braddock Bay Bird Observatory. Datasets contain data on each bird’s sex, age, weight, tarsus length, wing chord, and other notes. Each bird’s subcutaneous fat load was qualitatively scored using a standardized scoring system ranging from 0 (no visible fat) to 5 (fat overflowing and greatly distended). Collected waste samples were freeze-dried and homogenized before elemental analyses.
Files and variables
File: songbird_waste_elemental_measurements.csv
Description: All waste samples were first analyzed for % Carbon (C) and % Nitrogen (N) content using a Carlo Erba NC2500 elemental analyzer. We examined the relationship between a bird’s waste measurements and trophic feeding position by conducting analyses of stable isotope δ15N using a Thermo Delta V isotope ratio mass spectrometer (IRMS).
Variables
- sample_ID: The number the data collector assigned to each bird in chronological order.
- common_name: The common or local name of the bird species.
- species: The four-letter bird banding species code, which is an abbreviation of the common name.
- scientific_name: The scientific name of the bird in Genus species format.
- season: Fecal samples were collected in one of two seasons (fall or spring).
- date: The date the waste sample was collected in month/day/year format.
- location: All waste samples were collected at the Braddock Bay Bird Observatory (BBBO).
- time_in: The time the bird entered the waste collection bag.
- time_released: The time the bird was released into the wild from the waste collection bag.
- time_total: The total amount of time the bird spent in the waste collection bag.
- time_total_minutes: The total amount of time the bird spent in the bag expressed in minutes.
- fecal_sample_weight_g: The weight of the fecal sample in grams (g) after it was freeze-dried and homogenized.
- waste_release_rate_g/hr: The rate of waste release in grams per hour (g/hr), which was calculated by dividing the dry weight of waste (g) by the amount of time the bird spent in the bag (hr).
- C_percent: The percent Carbon (C) content of the waste sample.
- N_percent: The percent Nitrogen (N) content of the waste sample.
- C:N_ratio: Carbon to Nitrogen ratio.
- X15N_vs_air: Stable isotope δ15N relative to atmospheric N₂ (air) in per mille (‰).
- age: Bird banding age codes. HY= Hatch Year; AHY= After Hatch Year; SY= Second Year; ASY= After Second Year.
- sex: Bird banding sex codes. M= Male; F= Female; U= Unknown
- wing_chord: Measurement of a bird's wing length in millimeters (mm).
- tarsus_length: Measurement of a bird's tarsus in millimeters (mm).
- fat_score: Assessment of a bird's body fat using a standardized scoring system from 0 (no visible fat) to 5 (fat overflowing and greatly distended).
- bird_weight_g: Measurement of a bird's body mass in grams (g).
File: songbird_waste_phosphorus_analyses.csv
Description: After completing C, N, and isotope analyses, waste samples from 31 individual birds (from 15 species and 5 families) were analyzed for Phosphorus (P) concentrations and other elements using Agilent 8900 triple quadrupole inductively coupled plasma mass spectrometry (ICP-MS).
Variables
- sample_ID: The number the data collector assigned to each bird in chronological order.
- common_name: The common or local name of the bird species.
- species: The four-letter bird banding species code, which is an abbreviation of the common name.
- scientific_name: The scientific name of the bird in Genus species format.
- season: Fecal samples were collected in one of two seasons (fall or spring).
- date: The date the waste sample was collected in month/day/year format.
- location: All waste samples were collected at the Braddock Bay Bird Observatory (BBBO).
- time_in: The time the bird entered the waste collection bag.
- time_released: The time the bird was released into the wild from the waste collection bag.
- time_total: The total amount of time the bird spent in the waste collection bag.
- time_total_minutes: The total amount of time the bird spent in the bag expressed in minutes.
- fecal_sample_weight_g: The weight of the fecal sample in grams (g) after it was freeze-dried and homogenized.
- waste_release_rate_g/hr: The rate of waste release in grams per hour (g/hr), which was calculated by dividing the dry weight of waste (g) by the amount of time the bird spent in the bag (hr).
- Na_g/g: The sodium (Na) content of the waste sample measured in grams of sodium per gram of sample (g/g)
- Mg_g/g: The magnesium (Mg) content of the waste sample measured in grams of sodium per gram of sample (g/g)
- K_g/g: The potassium (K) content of the waste sample measured in grams of sodium per gram of sample (g/g)
- Ca_g/g: The calcium (Ca) content of the waste sample measured in grams of sodium per gram of sample (g/g)
- S_g/g: The sulfur (S) content of the waste sample measured in grams of sodium per gram of sample (g/g)
- P_g/g: The phosphorus (P) content of the waste sample measured in grams of sodium per gram of sample (g/g)
- C_percent: The percent Carbon (C) content of the waste sample.
- N_percent: The percent Nitrogen (N) content of the waste sample.
- C:N_ratio: Carbon to Nitrogen ratio.
- P_percent: The percent Phosphorus (P) content of the waste sample, which was measured by multiplying P (g/g) by 100.
- C:P_ratio: Carbon to Phosphorus ratio.
- N:P_ratio: Nitrogen to Phosphorus ratio.
- X15N_vs_air: Stable isotope δ15N relative to atmospheric N₂ (air) in per mille (‰).
- age: Bird banding age codes. HY= Hatch Year; AHY= After Hatch Year; SY= Second Year; ASY= After Second Year.
- sex: Bird banding sex codes. M= Male; F= Female; U= Unknown
- wing_chord: Measurement of a bird's wing length in millimeters (mm).
- tarsus_length: Measurement of a bird's tarsus in millimeters (mm).
- fat_score: Assessment of a bird's body fat using a standardized scoring system from 0 (no visible fat) to 5 (fat overflowing and greatly distended).
- bird_weight_g: Measurement of a bird's body mass in grams (g).
Code/software
Notebook: R (version 4.3.1)
Loaded packages: dplyr, tidyr, car, lme4, nlme, ggplot2, ggpubr, lmtest, patchwork, gridExtra, emmeans, readr, lmerTest, performance, ggeffects