Climate Change May Affect Fatal Competition between Two Bird Species

Area of Science:

• Ecology
• Climate Change Biology
• Ornithology

Background:

• Climate warming impacts species' phenologies, affecting interspecific interactions.
• Differential phenological shifts can alter competitive and facilitative outcomes between species.
• Evidence for altered competition due to phenological shifts within trophic levels is limited.

Purpose of the Study:

• To investigate mechanisms of climate change-driven fatal interactions between great tits (Parus major) and pied flycatchers (Ficedula hypoleuca).
• To assess how altered phenologies and population densities affect interspecific competition and mortality.
• To determine the population-level consequences of this fatal competition.

Main Methods:

• Comparative analysis of breeding phenology shifts in response to spring temperatures for both species.
• Monitoring of flycatcher mortality rates in relation to flycatcher arrival timing and great tit density.
• Assessment of population dynamics and the role of surplus males in mortality.

Main Results:

• Spring temperature advanced great tit phenology more than flycatcher phenology.
• Great tits killed more flycatchers when flycatcher arrival overlapped with peak tit nesting.
• Flycatcher mortality increased with higher great tit densities, particularly affecting late-arriving males, but showed no population-level consequences.

Conclusions:

• Climate change may alter the balance of fatal competition between these species, with potential for divergence or intensification.
• The great tit-flycatcher population appears buffered against detrimental effects of current interspecific competition.
• Future climate change, especially warmer winters favoring residents, could exacerbate competition impacts if population buffers diminish.