Nationwide trophic cascades: changes in avian community structure driven by ungulates

Area of Science:

• Ecology
• Wildlife Conservation
• Ornithology

Background:

• Ungulate populations have fluctuated significantly, causing ecosystem-wide effects.
• Previous studies on these effects often lack broad spatial and temporal scope.
• Woodland ecosystems are particularly vulnerable to changes in herbivore populations.

Purpose of the Study:

• To compare national-scale population trends of deer-sensitive and deer-tolerant birds in Britain.
• To investigate the association between deer population trends and bird community changes.
• To assess the cascading effects of ungulate population dynamics on avian communities.

Main Methods:

• Analysis of multi-species composite population trends for deer-sensitive and deer-tolerant birds (1994-2011).
• Comparison of bird community trends against national woodland deer population trends.
• Statistical association analysis between deer population divergence and bird community shifts.

Main Results:

• A 46% increase in composite deer population trends was observed.
• Deer-sensitive bird communities, dependent on understory vegetation, declined significantly more than deer-tolerant bird communities.
• A striking association was found between increasing deer populations and declining deer-sensitive bird populations.

Conclusions:

• Changes in deer populations directly impact woodland bird communities.
• Ungulate population dynamics can drive community restructuring at other trophic levels.
• Conservation efforts may need to more thoroughly consider ungulate impacts on other taxa.