Colour-ring wear and loss effects in citizen science mark-resighting studies

Abstract

Background: Ring wear and loss may have important consequences for mark-recapture studies that aim to estimate survival trends. Our study quantifies the rates of wear and loss from a long-running colour-ringing project of the Eurasian Oystercatcher (Haematopus ostralegus) in the Netherlands. Methods: Our analysis included 8909 colour-ringed oystercatchers with 118,071 resightings, predominantly ringed and observed by citizen scientists. We quantified how ring wear and loss may vary with ring colour and age, and how this may impact resighting probabilities. We then determined how ring loss may impact survival estimates and resighting probabilities of mark-recapture models by simulating four scenarios of how citizen scientists may resight and report birds with lost colour rings. Results: Annual rates of colour ring loss averaged 2.5% compared with 1% for ring wear, but lost rings also had a higher reporting probability (31.2%) than worn rings (10.3%). Lost rings may not directly impact survival estimates since 50% of oystercatchers with lost rings could still be uniquely identified. Ring wear and loss rapidly increased between 10 and 15 years after ringing. Rates of ring loss were comparable amongst ring colours, but the wear rate appeared higher for red and white rings compared to other colours. Rates of ring wear and loss varied significantly amongst different regions in our study, which were characterised as having different habitat features. Differential rates of ring wear may have important implications for studies conducted over large geographical scales or of multiple species. Conclusions: Based on simulations of ring loss in our population, estimates of apparent survival may be 0.3-1.2% lower whilst the impact of ring wear was deemed even lower. We developed a table of recommendations containing advice for ring fitting, data collection, study design, and mark-recapture analyses, so that future colour-ringing studies can benefit from our experiences in collecting and analysing data of ring wear and loss through citizen science.

The demographic causes of population change vary across four decades in a long‐lived shorebird

“…In line with life history theory of long‐lived species, oystercatchers likely prioritize their own survival over reproduction (Ens et al, 2014 ; Gaillard & Yoccoz, 2003 ; Pfister, 1998 ). Adult survival can vary considerably from 1 year to the next due to, for example, severe winters (Appendix S1 ; Allen et al, 2019 a; van de Pol et al, 2010c ), but over longer temporal scales (e.g., decades), we show that adult survival had low temporal variation as expected by the environmental canalization hypothesis. We also found low levels of individual variation in adult survival based on our state variables of lay date and sex, neither of which were important for explaining variation in adult survival and instead most variation was explained by breeding status, although variation in non‐breeder survival had minimal influence on λ (Figure 2 ; Appendix S1 ).…”

“…Oystercatchers have been ringed with unique color codes and ongoing research has maintained a high (>90%) proportion of color‐ringed individuals in the breeding population. Low rates of ring wear, along with active replacement of worn rings, mean that almost all color‐ringed individuals remain identifiable (Allen et al, 2019b). At the start of the project (1983), the local breeding population was initially saturated although the Wadden Sea population was still growing (van de Pol et al, 2010c; Ens et al, 2014).…”

Exceptionally high apparent adult survival in three tropical species of plovers in Madagascar

“…Lost rings were replaced on recaptured birds wherever possible. Colour ring loss over time can be a minor issue, making subsequent apparent survival estimates up to 1.2% more conservative (Allen et al 2019). In addition to standard measurements, we also collected blood samples from 63.5% to 76.9% of captured birds for genetic sexing.…”

Current applications and future promise of genetic/genomic data for conservation in an Aotearoa New Zealand context

“…Four key practices when establishing an effective pedigree management system include: using a robust system to identify individuals to ensure correct assignment of relationships (Allen et al, 2019); collecting genetic data from founding individuals to evaluate relatedness (Bergner et al, 2014;Hogg et al, 2019); the use of monitoring technologies (e.g., cameras, RFID tags; Bonter & Bridge, 2011) particularly when working with wild populations to ensure accurate breeding records; and collecting tissue or blood samples from all individuals for downstream genetic analyses in the case of any uncertainties or known errors (Frasier et al, 2009;Ryder & Feistner, 1995). This can also facilitate downstream pedigree evaluation to assist with error detection and correction.…”