DOI: 10.5061/dryad.jq2bvq8q6
title: Diet, phenology, and body size shape nutrient release by songbirds

description: 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.
description: # Diet, phenology, and body size shape nutrient release by songbirds
 Dataset DOI:
 [10.5061/dryad.jq2bvq8q6](https://doi.org/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