# Survival Prospects of Wild Birds Depending on the Type of Injury and Other Stressors Leading to Hospitalisation: A Long-Term (1988–2020) Retrospective Study from an Urbanised Area of the Alps

## TL;DR

This study examines the survival rates of wild birds in an Austrian zoo based on injury types and other stressors over 33 years.

## Contribution

The study provides long-term insights into bird rehabilitation success influenced by injury types and urban stressors.

## Key findings

- Orphaned birds and those with unknown admission reasons had the highest survival rates (60%).
- Birds with physical injuries, window collisions, or cat attacks had the lowest survival rates (37%).
- Areal insectivores and waterbirds had higher survival rates compared to small songbirds and woodpeckers.

## Abstract

We analysed the Innsbruck Alpenzoo database of wild birds that were rescued in the densely populated Inn Valley around Innsbruck, Austria, and admitted to the zoo over a period of 33 years (1988–2020). In this publication, we focus on the outcomes of rehabilitation efforts by the zoo staff. Our objectives are (a) to explore the general survival chances of different bird groups, and (b) to examine how the reasons for admission influence rehabilitation success in terms of survival rates and the duration of care required. Orphaned birds, specimens that had become entangled in man-made structures, and birds with unknown reasons for admission had the best survival rates, while birds with severe physical injuries, victims of window collisions, and cat attacks had the lowest survival rates. Rates were highest among areal insectivores and waterbirds, and lowest among small songbirds and woodpeckers, which suffered disproportionately from the consequences of collisions. The overall survival rate of hospitalised birds was higher, and the duration of care required was shorter at Innsbruck Alpenzoo than at most other rehabilitation centres. We attribute this mainly to the professional care and varied diet provided to the patients. We also discuss the problems and limitations of wild bird care for zoo staff in addition to their daily tasks.

We analysed data collected at the Innsbruck Alpenzoo (Tyrol, Austria) over 33 years (1988–2020). We examined data from 4542 wild birds of 137 species that were rescued in the increasingly urbanised and densely populated Inn Valley around Innsbruck and examined the outcome of hospital treatment (survival or death); for a subgroup of 3440 birds, we examined the length of stay at the zoo. The birds were divided into nine different groups, and the reasons for admission were divided into nine categories to analyse how the reasons for admission and membership of a bird group influences rehabilitation success and the duration of care required. Orphaned birds, birds that had become entangled in man-made structures, and birds with unknown reasons for admission had the best survival rates (60%), while birds with physical injuries, victims of collisions, and attacks by cats had the lowest survival rates (37%). Survival rates were highest among areal insectivores (66%) and waterbirds (62%), and lowest among small songbirds (45%) and woodpeckers (<39%), which suffered disproportionately from the consequences of window collisions. The overall survival rate of hospitalised birds (51%) was higher, and the duration of care required (median 11 days) was especially shorter at Innsbruck Alpenzoo than at most other rehabilitation centres. We attribute this mainly to the professional care and varied, group-specific diet provided to the patients, which we describe in detail. We also discuss the problems and limitations of wild bird care for zoo staff in addition to their daily tasks. Thereby, it became apparent that the retirement of experienced bird carers at the beginning of the study period and the subsequent steady changeover of staff members had a negative impact on success rates.