RAS results

In total, 188 RAS projects were active in 2023. Data from historical projects and active projects that have been running successfully for five or more years are included in the analyses of the national results presented here.

The RAS analyses generate two parameters: survival rates and re-encounter rates. The survival rates indicate the proportion of birds that survive and return to the site to breed each year, while the re-encounter rates provide a measure of the probability of a bird’s presence being detected should it have survived and returned; the higher the re-encounter rate, the more precise the survival estimate.

The table and graphs below present the mean re-encounter rates, survival rates and survival trends for all species for which we have sufficient data to produce a trend. For more information about the RAS results, please see the Explanatory Notes pages.

• For more information about the RAS results, please see the RAS Results Explanatory Notes. 

Summary results

The summary table of active and historical RAS projects shows, for each species, how many projects ran in 2023 and how many projects contributed to each trend.

It is apparent from these data that some species, e.g. Pied Flycatcher, House Sparrow, lend themselves well to RAS and uptake has been very high.  Priority species for future RAS recruitment are those for which established studies are producing reliable survival trends but currently only at a few sites; these include Barn Owl, Dipper, Mute Swan, Starling, Swallow and Tree Sparrow.

The other table below summarises the mean survival and re-encounter rates by species. Re-encounter rates may be heavily influenced by methodology and several general patterns are apparent:

• Species that are caught on or near nests/nestboxes, such as Dipper, Barn Owl and Pied Flycatcher, tend to exhibit higher re-encounter rates for females as they spend more time incubating and brooding the contents than the males do.
• Species caught using tape lures, e.g. Willow Warbler, Sedge Warbler, tend to exhibit higher re-encounter rates for males.
• Colony nesters, such as seabirds and Sand Martins, tend to have lower re-encounter rates as it is much harder to systematically target individual birds.

While not summarised in this table, re-encounter rates are also generally higher in studies using colour rings, e.g. Bearded Tit, Kittiwake, Shag and Wood Warbler, but this is obviously dependent on resighting effort.

Species specific results

Select a species from the drop-down list.

• For more information about how to interpret the data shown on the RAS results graphs, please see the RAS Results Explanatory Notes.