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Clouded Yellow (Colias croceus)

On this page, we have made available all the information we have for this species

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Picture of Clouded Yellow
© Eddie John

The Clouded Yellow is a highly mobile species that occurs in Britain as a migrant from southern Europe in highly variable numbers annually. It breeds on vetches and clovers in open sunny situations. It has been recorded surviving our British winters on the south coast in recent years. (For further details on this species see

Family : Pieridae

Status : Stable

Status details :
Status since 1979 is Stable with a increase of 284%
Status over the last 20 years is Stable with a decrease of -57.3%
Status over the last 10 years is Stable with a increase of 419%

Log collated index plot

Species Log Collated Index Plot

This chart shows the index of abundance (LCI = Log Collated Index) over time. It shows fluctuations in populations from year to year, and is scaled so that the average index over the whole series is equal to 2 (horizontal line). For greater detail about how this index is derived, click on the green question mark above.

Trend description :
This migrant species is recorded more and more regularly on UKBMS transects and it has been suggested that it may now successfully overwinter in areas of suitable habitat in southern England. Numbers on UKBMS sites vary considerably from year to year, the huge fluctuations in the collated index plot demonstrating the good migrant years where some sites record double, sometimes triple, figure numbers. In 2000 Clouded yellow produced a three figure index on four different UKBMS sites. The data show no significant trend. However, as the collated index plot shows, there has been a large increase since monitoring began and the lack of significance is likely a result of the recent run of poor migrant years.

This map shows the distribution between 1995 and 2016. Data is derived from the Butterflies for the New Millenium dataset via the NBN Gateway

Phenology plot
Species Phenology Plot

Phenology plot

This chart shows the average number of butterflies seen on transects between Arpil and October across all sites (fitted values from a Generalised Additive Model). The blue line gives average counts over the full BMS series (1976 to date) and the red line gives the average for the last year.

Species abundance map


This map shows symbols for the mean abundance at transect sites, with the colour of the symbol reflecting the level of abundance. Means are over all years. Grey background squares are the occupied cells as shown by the Butterflies for the New Millenium over the previous ten year period.


In total, Clouded Yellow has been recorded from 539 transects in the Butterfly Monitoring Scheme. Of these, annual indices of abundance have been calculated from 667 sites, with an average index of 2 individuals per site.

For 350 of these sites, Clouded Yellow has been recorded well enough to calculate annual indices of abundance in more years, allowing trends to be calculated.

In 2019, 2787 individuals were recorded from 296 sites, producing annual indices at 232 of these.

The UK Butterfly Monitoring Scheme is organized and funded by Butterfly Conservation (BC), the UK Centre for Ecology and Hydrology (CEH), the British Trust for Ornithology (BTO), and the Joint Nature Conservation Committee (JNCC). The UKBMS is indebted to all volunteers who contribute data to the scheme.