Data from: Assessing factors associated with changes in the numbers of birds visiting gardens in winter: are predators partly to blame?
| Main Authors: | Swallow, Ben, Buckland, Stephen, King, Ruth, Toms, Mike |
|---|---|
| Format: | info dataset eJournal |
| Terbitan: |
, 2020
|
| Subjects: | |
| Online Access: |
https://zenodo.org/record/4069016 |
Daftar Isi:
- The factors governing the recent declines observed in many songbirds have received much research interest, in particular whether increases of avian predators have had a negative effect on any of their prey species. In addition, further discussion has centred on whether or not the choice of model formulation has an effect on model inference. The study goal was to evaluate changes in the number of 10 songbird species in relation to a suite of environmental covariates, testing for any evidence in support of a predator effect using multiple model formulations to check for consistency in the results. We compare two different approaches to the analysis of long-term garden bird monitoring data. The first approach models change in the prey species between 1970 and 2005 as a function of environmental covariates, including the abundance of an avian predator, whilst the second uses a change-change approach. Significant negative relationships were found between Eurasian sparrowhawk Accipiter nisus and three of the 10 species analysed, namely house sparrow Passer domesticus, starling Sturnus vulgaris and blue tit Cyanistes caeruleus. The results were consistent under both modelling approaches. It is not clear if this is a direct negative impact on the overall populations of these species or a behavioural response of the prey species to avoid feeding stations frequented by sparrowhawks (which may in turn have population consequences, by reducing available resources). The species showing evidence of negative effects of sparrowhawks were three of the four species most at risk to sparrowhawk predation according to their prevalence in the predator's diet. The associations could be causal in nature, although in practical terms the reduction in the rate of change in numbers visiting gardens accredited to sparrowhawks is relatively small, and so unlikely to be the main driver of observed population declines.
- GBFS_cleaned_70_06Cleaned data from the British Trust for Ornithology's Garden Bird Feeding Survey from 1970/71 to 2005/06 on ten species of potential avian prey and Sparrowhawks. These data are the basis for all analyses in the accompanying manuscript. In addition to mean weekly maxima for each site, year and species, the dataset also includes the following variables: site reference number; year of observation (1=1970/71, 36=2005/06); whether site is rural or urban (rural = −1 and suburban/urban = +1); northing and easting of site; minimum temperature over observation months (not used in manuscript); and normalised number of days of ground frost over observation months. Variable 'ransite' determines the unique site numbers, accounting for sites that drop out and rejoin the survey in a later year. These are used in the specification of the random effect terms in the model. Species are: SPARR: Eurasian Sparrowhawk (Accipiter nisus); BLABI: Eurasian Blackbird (Turdus merula); BLUTI: Eurasian Blue Tit (Cyanistes caeruleus); COLDO: Eurasian collared dove (Streptopelia decaocto); CHAFF: Common chaffinch (Fringilla coelebs); COATI: Coal Tit (Periparus ater); GREFI: European greenfinch (Chloris chloris); GRETI: Great tit (Parus major); HOUSP: House sparrow (Passer domesticus); ROBIN: European robin (Erithacus rubecula); STARL: Common starling (Sturnus vulgaris).