
BTO Garden BirdWatch: Weekly butterfly abundance data for modelling trends in UK 
gardens (v1.0)
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Kate E Plummer (kate.plummer@bto.org) 2023-05-24

This data package has been used to estimate annual abundance indices and trends
for butterflies in UK gardens. 'bfly_counts_per_week' presents the butterfly 
abundance data, and the additional files provide supporting information about 
species and sites. Dataset descriptions are given below.



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ABOUT THE DATA 

Data have been collected as part of the British Trust for Ornithology (BTO) 
Garden BirdWatch (GBW) survey. GBW is a structured, citizen science monitoring 
programme whereby volunteers record weekly abundances of various bird, 
invertebrate, mammal, reptile and amphibian species in (predominantly suburban
and rural) gardens. See www.bto.org/gbw for further information about the 
survey.

The data are pre-filtered to meet criteria for inclusion in the modelling
of butterfly species trends, as described by Plummer et al (2023).
A brief summary of the key characteristics of the data is given below, but 
please refer to the paper for a more comprehensive explanation.

Characteristics of the data
  * The first year in the time series is 2007
  * An annual survey season is 35 weeks, from beginning March - end October
  * Only GBW sites with >=5 weeks of non-zero butterfly counts are included
  * GBW sites are distributed across the UK, Isle of Man and Channel Isles
  * Extreme outlying counts are removed
  * Only species recorded in >=15 sites each season are included

Reference
  Plummer KE, Dadam D, Brereton T, Dennis EB, Massimino D, Risely K, 
  Siriwardena GM & Toms, MP (2023). Trends in butterfly populations in UK 
  gardens - new evidence from citizen science monitoring. 
  Insect Conservation and Diversity. https://doi.org/10.1111/icad.12645
	

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DATASET:      bfly_counts_per_week.csv
	
Description:  Butterfly weekly abundance per Garden BirdWatch site for Mar-Oct 
              (35 weeks) from 2007 onwards. 5-letter codes are used for
              species names, as described in the bfly_species_list.csv
              dataset (below).
				
  VARIABLE         DESCRIPTION
  site_id          Garden BirdWatch site identity
  week             Survey week (1-35)
  date             Start of survey week (yyyy-mm-dd)
  year             Year	
  xlask            Weekly maximum count for Large Skipper
  ...              ...
  ...              ...
  xring            Weekly maximum count for Ringlet
  

	
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DATASET:      bfly_site_list.csv
	
Description:  Site-specific spatial information for the GBW sites represented 
              in the dataset based on British National Grid (BNG). 

  VARIABLE         DESCRIPTION
  site_id          Garden BirdWatch site identity
  tenkm            10-km grid square (BNG) in which site is situated
  gridref          1-km grid square (BNG) in which site is situated



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DATASET:      bfly_species_list.csv
	
Description:  Species-specific information for the butterfly species 
              represented in the dataset. 

  VARIABLE         DESCRIPTION
  taxorder         Taxonomic order
  species          Species 5-letter code
  spname           Common name
  sciname          Scientific name
  

	
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