Each bird that is submitted to the PBMS is given a postmortem examination during which approximately 60 macroscopic observations and measurements are made.

These observations can be used to generate population health indices that can inform us about the status of recruitment and survival, physiological stress, and nutritional status in the population.  

Changes in these indices may indicate where the population is under stress and therefore highlight where we might focus our monitoring to determine if chemical exposure is contributing to the changes observed.

For each species listed below a range of population health indices are calculated to help assess the state of predatory birds submitted to us.

These health indices were analysed for each species over the period 2000 to 2016. For each index we determined an average and 95% prediction intervals for indices that had not changed over time and trend lines for indices that had changed. Data for subsequent years have been added to the graphs for each index. Data for birds in the current year are added as the birds are necropsied and so the data are subject to update as new birds are examined.

The intention is that these health indices can be used to identify trends that may indicate a significant change in the status of the population studied.

Graphs of health indices with trend lines are available for the following species:

 

Summary of recent findings

Note: When referring to demographic groups within the population, we mean the age and sex of the birds.

Sparrowhawks

Based on PBMS data up to and including 2019

Demographic ratios (age and sex) within sparrowhawks received by the PBMS remain within the 95% prediction intervals (95%PI) established in baseline years (2000 to 2016). This means there has not been a significant change in the demographic structure of the sparrowhawks received by the PBMS.

Body weight, putative cause of death, fat score, and condition index were within predicted range for all the demographic groups analysed. This indicates that the nutritional status of the sparrowhawks received by the PBMS was consistent through baseline years and has not significantly changed from that baseline in subsequent years. N.B. There were insufficient male adult sparrowhawks received each year to calculate a baseline. These observations indicate that food availability has been consistent through both baseline years and since 2017.

Fluctuating asymmetry in the 10th primary feather weight (FAP10) within adults (females and males combined) between 2017 and 2019 remained generally consistent, with no time trend evident, and within the prediction range. 2019 juvenile female birds had showed higher average FAP10 than baseline years. Male juvenile birds showed an increase in FAP10 in baseline years, and from 2017 to 2019 data were consistent with this trend. Increases in FAP10 may indicate that birds have been subject to physiological stress during the development of flight feathers. Our observations indicate that juveniles (particularly male) may be subject to increasing levels of physiological stress during feather flight development (i.e. during the fledging period).