Optimal conservation planning for migratory animals: integrating demographic information across seasons

Abstract

Conservation strategies for migratory animals are typically based on ad-hoc or simple ranking methods and focus on a single period of the annual cycle. We use a density-dependent population model to examine one-time land purchase strategies for a migratory population with a breeding and wintering grounds. Under equal rates of habitat loss, we show that it is optimal to invest more, but never solely, in the habitat with the higher density dependence to habitat cost ratio. When there are two habitats that vary in quality within a season, the best strategy is to invest only in one habitat. Whether to purchase highor low-quality habitat depends on the general life history of the species and the ratio of habitat quality to habitat cost. When carry-over effects are incorporated, it is almost always optimal to invest in high-quality habitat during the season that produces the carry-over effect. We apply this model to a threatened warbler population and show the optimal strategy is to purchase more breeding than wintering habitat despite the fact that breeding habitat is over ten times more expensive. Our model provides a framework for developing year-round conservation strategies for migratory animals and has important implications for long-term planning and management.

Prioritizing tropical habitats for long-distance migratory songbirds: an assessment of habitat quality at a stopover site in Colombia

“…This dependence on multiple sites, often separated by thousands of kilometers, renders migratory birds especially vulnerable to widespread anthropogenic change (Newton 2004, Faaborg et al 2010) and likely explains the persistent global declines documented in this group (Sanderson et al 2006, Holmes 2007. Full life-cycle approaches to conserving migratory birds therefore require detailed knowledge of all aspects of the life cycle (Sheehy et al 2010), yet, in the Americas, our lack of knowledge of stopover habitat, particularly in the tropics, is a major limiting factor for hemispheric initiatives aimed at reversing population declines (Faaborg et al 2010). …”

Non-breeding season habitat quality mediates the strength of density-dependence for a migratory bird

“…For example, if overwinter survival is regulated by conspecific density, loss of high-quality tropical habitats could shape the strength and form of density dependence [24]. Management of migratory bird populations requires population models that encompass the full annual cycle, parametrized with estimates of seasonal density dependence [32][33][34].…”

Factors driving territory size and breeding success in a threatened migratory songbird, the Canada Warbler

“…Given the emerging information on demography at either end of the annual cycle now requires understanding how individuals are connected between breeding and nonbreeding seasons because it influences both population dynamics (Webster et al 2002) and informs conservation planning (Martin et al 2007). Ultimately, integrating demography and migratory connectivity across the annual cycle can identify which threats contribute the most to population viability (Flockhart et al 2015) to prioritize costeffective actions to mitigate population declines in threatened migratory songbirds (Sheehy et al 2010). …”