Concrete habitat: Impervious surface and avian fitness decline in two urban adapters
Data files
Mar 25, 2024 version files 50.90 KB
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BT_fled.txt
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GT_fled.txt
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README.md
Oct 18, 2024 version files 51.16 KB
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BT_fled.txt
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GT_fled.txt
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README.md
Abstract
The conversion of natural habitats to impervious surfaces in cities affects biotic and abiotic attributes of urban ecosystems. Detailed information on the gradual influence of impervious surfaces on reproductive output, however, is lacking. Using five years of nestbox-breeding great tit and blue tit data collected across various habitat types within and outside a Central-Eastern European capital city, we quantified the impact of impervious surfaces on avian reproductive success. Impervious surfaces strongly and negatively covaried with the number of fledged young in both species: a 0 to 50% increase in impervious surface within 100 m of the nest was associated with 3.56 fewer fledged offspring in great tits (95% CI: -4.85, -2.27) and 2.91 fewer fledged offspring in blue tits (95% CI: -4.26, -1.56), thus halving the reproductive output of two widespread urban species. These results provide benchmark values of avian productivity for ecologists and urban policy makers, and for the management of urban areas.
README: Concrete habitat: Impervious surface in nest vicinity is associated with avian fitness decline in two urban adapters
We included data and codes used for the analyses presented in the manuscript entitled "Concrete habitat: Impervious surface in nest vicinity is associated with avian fitness decline in two urban adapters" by Michela Corsini and Marta Szulkin.
Description of the Data and file structure
Data are included for each species. The file GT_fled includes data for fledglings analyses in Great tits, BT_fled includes data for fledglings analyses in Blue tits.
The text file GT_fled includes data on the total number of fledglings per breeding event. Nests were checked 25 days after hatching (hatching date was recorded as Day 1) to record ho many ringed birds died.
The R-file entitled "Fled_analyses_ISA_Corsini2024" includes all codes for models (glms with quasi-Poisson distribution) and plots (built in ggplot2).
Labels:
Year: Includes the year of the study: 2017, 2018, 2019, 2020 or 2021
Site: CMZ: Urban woodland Jewish cemetery, KPN: Kampinos national park, OLO: residential area Las Olszyna, MUR: residential area Muranow, POL: Urban park Pole Mokotowskie, UNI: University campus - office area, LOL: Urban woodland Las Olszyna. All sites were located in Warsaw or in its outskirts, Poland.
BroodNr: Brood number, standardized by picking the first broods of the season. Only first broods initiated within 30 days after the first brood recorded for each species in a given year and site were included in the study (Van Balen 1973).
NestboxID: id of the nestbox.
Species: GT= Great tit, BT=Blue tit.
Lay date: Date of the first egg laid per breeding event. Julian date: 1st of April as 1 every year.
CS: Clutch size. Total number of eggs per breeding event.
NrHatchlings: Total number of hatched birds per breeding event.
BroodSize15: Total number of nestlings that were alive in the nest 15 days after hatching.
Ring_fem: Ring id of the adult female.
Mass_Fem: Body mass of adult female in grams. It was measured between 10 and 14 days after the first nestling of the brood hatched.
ISA: Percentage of Impervious Surface Areas measured in a 100m radius around each nestbox. We used a 20m resolution raster map layer downloaded from the web site Copernicus Land Monitoring. Bufer analyses were run in qGIS.
Fledglings: Total number of fledged nestlings per breeding event. Broods were checked 25 days after hatching.
hatch_ratio: Ratio of hatched birds over the number of eggs laid per breeding event.
Fledg_ratio: Ratio of fledged birds over the number of hatched nestlings per breeding event.
ISAlev: ISA level measured as low or high after taking the median value of ISA across all the set up.
LayDate_sc: Scaled Lay date.
Mass_Fem_sc: Scaled mass of adult female.
CS_sc: Scaled clutch size
ISA_sc: scaled ISA
The text file entitled Fledg_ISA_DataPreparation contains all the steps to prepare the datasets described above for the analyses. Labels here reported are analogous to those indicated above.
Methods
Study area
Data were collected from 500 Schwegler woodcrete-nestboxes (type 1b, with a 32 mm-diameter entrance hole, suitable for great tits and blue tits) set in a 50m grid within eight study sites in and outside the city of Warsaw, Poland (Fig.1). Our set up comprehends study sites from highly urbanized locations close to the city center (e.g., an office area and two residential sites – blocks of flats typical of post-war Eastern European architecture, built in the late 40’s and 50’s of the 20th century) and from green urban spaces (an urban park and two urban woodlands). The study system is also composed of two study areas located outside the city: a suburban village and a natural forest. More details relative to each study site location are reported in earlier publications (Corsini et al. 2019, 2020).
Breeding data
Great tit and blue tit breeding data were collected for five years (2017-2021). Each year, nestboxes were inspected weekly, starting from March until mid-July with the only exception of one urban woodland (the cemetery), which could not be visited regularly in 2020 due to pandemic-related access restrictions (Corsini et al. 2022). Overall, such visiting frequency allowed for estimating the date of the first egg laid and clutch size, as these species lay one egg daily. Hatching date was determined by checking the nestboxes one day before expected hatching or every other day after that, until hatching occurred. Parents were caught, aged (as first year breeders or older), measured, and ringed when nestlings were 10-13 days old. Fifteen days after hatching, alive nestlings were counted, individually weighed and ringed. Twenty-five days after hatching, nestboxes were checked to record fledging success. Only first broods initiated within 30 days after the first brood recorded for each species in a given year and site were included in the study (Van Balen 1973).
Quantifying urbanization
Urbanization was measured as the percentage of Impervious Surface Area (ISA) in a 100m-radius from each nestbox. Namely, a 20-m pixels resolution ISA-raster file was downloaded from Copernicus Land Monitoring Services (https://land.copernicus.eu/sitemap), and averaged for each nestbox via buffer-analyses in qGIS v.3.10 (Team 2016) (see Szulkin et al. (2020)). The ISA layer contained all built-up areas which replaced original natural cover with impervious or any other artificial surface. The 100m-radius was selected based on the food foraging distance covered by blue tit parents while feeding the nestlings (Tremblay et al. 2004).
Statistical analyses
Statistical analyses were performed in R (v. 4.1.2). Because of species-specific differences in life-history, great tits and blue tits were analyzed separately. To test the association between number of fledged offspring and ISA, we fitted Generalized Linear Mixed Effects Models (GLMMs). Namely, we included all nests where at least one egg hatched. Because data were over dispersed, we used a quasi-Poisson error-structure. We included the continuous predictors ISA, Lay date (1st of April recorded as 1), and Female Body Mass (as heavier females produce larger clutches and start breeding earlier in the season (Perrins & McCleery 1989)). We also fitted Year (5 levels) as a fixed effect. When including Site (8 levels) as a random effect to control for inter-site variation in avian breeding, we found that the between sites variance was close to zero, and therefore removed it from the models. Interactions between Year and ISA, and between Lay date and Female body mass were tested and removed from the models if not significant. Further, as the influence of ISA on Clutch size may influence the variability in fledging success, we conducted supplementary analyses using the same structure as previously indicated, incorporating Clutch size as a continuous predictor in the models. Potential multicollinearity issues were verified using the vif-function (car package (Fox et al. 2012)), which always yielded values below 2. Plots were built in ggplot2 (Wickham 2011) after calculating predictions in ggeffects (Lüdecke et al. 2020). Unit decreases in fledged offspring were calculated using the function avg_comparisons in the package marginaleffects (Arel-Bundock, 2023).
Usage notes
We used R v.4.1.2 to analyze the data, Inkscape to visualize the final plots, and qGIS v.3.34.2 to run the buffer analyses and generate the map.