Project Overview

Many bird species are facing steep declines, due to threats from climate change, habitat loss and direct persecution. Raptors (birds of prey) are particularly vulnerable. As apex predators, they require high-quality habitats for nesting, roosting and foraging making them excellent environmental indicators. Consequently, they are heavily impacted by land-use change, habitat fragmentation, and novel human structures like wind farms.

While conservation strategies traditionally focus on the summer breeding season to boost population recruitment, the threats birds face during the winter remain a critical knowledge gap.

The threats facing Irish hen harriers

The hen harrier (Circus cyaneus) is one of around 11 raptor species found on the island of Ireland – and it is the fastest declining. With only around 106 breeding pairs remaining, the species is recognised as highly threatened and is protected under European law (EU Birds Directive).

In Ireland, hen harriers are year-round residents, typically moving from upland summer breeding grounds to lowland areas for the winter. While the exact drivers of their decline in Ireland are complex, evidence points strongly to land-use changes, such as shifts in agricultural practices and the reduction of wetlands.

Additionally, the expansion of conifer forestry acts as an ecological trap for hen harriers: while birds use young plantations to breed and forage, they cannot use them as the forest matures and closes over. In response to their decline, Ireland currently has eight designated Special Protection Areas (SPAs) for hen harriers - six for breeding populations and two for wintering populations.

The current project

This current postdoctoral project is a collaboration with the National Parks and Wildlife Service (NPWS) and builds on previous research conducted on Irish hen harriers at University College Cork. Using satellite tracking and winter roosting datasets collected during Dr. Alan McCarthy’s PhD project (supervised by Prof. John O’Halloran), alongside national breeding survey data, we are investigating the factors driving hen harrier decline across their entire annual cycle. Our key areas of focus are:

• Evaluating wintering habitat: Initial analyses reveal that suitable winter habitats are limited in Ireland and not fully protected. Wintering harriers continue to rely on young commercial forestry alongside traditional habitats.
• Assessing novel threats: We aim to model hen harrier movement patterns in direct response to threats such as wind farms and conifer plantations.
• Predicting extinction risk: We will use advanced population modelling to determine the exact threat levels and extinction risks facing the species.

This research aims to inform more effective, year-round conservation policies to save one of Ireland’s most iconic birds.

We will keep this page updated as analyses progress!

Project Team

Dr Anna Bracken (UCC)

Dr Paul Holloway (UCC)

Dr Sinead Cummins (NPWS)

Prof. John Quinn (UCC)