Spruce grouse, a non-gregarious and sparsely distributed forest bird, shows synchronous nesting

Area of Science:

• Avian Ecology
• Wildlife Biology
• Reproductive Ecology

Background:

• Spruce grouse (Dendragapus canadensis) reproductive timing and success are key indicators of population health.
• Understanding factors influencing hatch date synchrony is crucial for avian population dynamics.

Purpose of the Study:

• To analyze hatch date synchrony in spruce grouse across different densities and age structures.
• To determine the influence of adult grouse on yearling reproductive timing.
• To assess the relationship between hatch date span and juvenile production.

Main Methods:

• Field observations of spruce grouse in Canada over 17 years (1970-1990).
• Documentation of hatch dates, female densities, age-structure, and juvenile production rates.
• Experimental thinning of adult grouse to assess impacts on yearling nesting.

Main Results:

• Substantial hatch date synchrony was observed (67% of clutches hatched within 6.5-8.8 days).
• Synchrony was not correlated with female density or adult-yearling interactions.
• Yearling grouse hatched clutches earlier when adult densities were experimentally reduced.
• Juvenile production did not vary across the span of hatch dates.

Conclusions:

• Hatch date synchrony in spruce grouse is robust but not driven by density-dependent or adult-influenced mechanisms as predicted by some models.
• Experimental evidence suggests adults may suppress yearling nesting timing.
• Synchronous nesting in spruce grouse does not appear to confer an immediate adaptive advantage in terms of juvenile recruitment.