Waterbirds in the UK presents the results of the annual Wetland Bird Survey Report. It provides a single, comprehensive source of information on the current status and distribution of waterbirds in the UK for those interested in the conservation of the populations of these species and the wetland sites they use.

This report explores the impact on the direction and statistical confidence in the individual species trends from which the wild bird indicator is composed when including missing years in the dataset, using simulated subsets of real data from previous years. This report was prompted by the impacts of Covid-19 lockdown restrictions on survey effort.

When ringing birds it is usually important to standardise measurements so that sources of error are minimised. For example, trainee ringers are taught how to measure wing lengths in the most repeatable fashion. Measuring bird weight is usually much more straightforward. One situation where this may not be the case is during canon netting when large numbers of birds can be caught at once, but are weighed gradually as the birds are processed, potentially leading to biases. This paper examines this phenomenon using captures of Knot, Turnstone, Dunlin and Semipalmated Sandpiper in Delaware Bay, USA. As these waders were caught whilst actively feeding on the eggs of Horseshoe Crabs, there was the possibility that birds weighed first could be heavier due to having a gut full of eggs, whilst those weighed last may have digested/voided their gut contents prior to being weighed and so weigh relatively less. For sample bird catches birds were weighed repeatedly, from immediately after capture to up to four hours after capture. The study found that birds rapidly lost up to 5% of their body weight in the first 30 minutes, with weight loss much reduced thereafter. This weight loss was strongly correlated to the number of droppings birds produced in the keeping pens, indicating the reduction was related to processing of gut contents. The paper shows how body weights can be standardised to that expected if each bird was weighed at 30 minutes after capture. For large catches this can increase the apparent mean weight for the sample by up to 2%. The paper also discusses the situations in which standardising body weight measurements for time from capture may be necessary.