Small Population Effects

Small populations of species are at a great disadvantage due to the detrimental effects that can occur impacting their ability to survive within our ecosystem and the habitats that they live in. Four detrimental effects that can occur within a small population includes, genetic drift including inbreeding, population bottleneck and the founder effect, environmental and demographic stochasticity, and loss of evolutionary flexibility. The Kirtland Warbler, is one such species that is impacted due to its small population and its specific and isolated habitat within the Jack Pine, Pinus banksianna, in the lower northern Michigan territory, along with its upper peninsulas, Wisconsin and Canada (U.S. Fish & Wildlife Services).

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When a species population is reduced in size, it loses the rare alleles needed to make its species thrive in future generations (Primack), the loss or decline in the genotypes of a species creates weak offspring. Expanding on the population bottleneck we have the founder effect that is occurring, as populations become small and smaller we leave a select few to carry on the population through their breeding effects. Population bottlenecks have more of a pronounced effect when populations are reduced below ten individuals for several generations (Primack). Bottlenecks caused by catastrophic events or periods may have a rapid change in population, but species can overcome this bottleneck in future generations. The reason, in a rapid or mass removal of a species those that remain, have not suffered from genetic drifting or loss of alleles and those small in number the species remains strong. When the habitat is viable for reproduction, the species has a better chance of recovering naturally in the

When their habitat is conducive, their nesting and breeding habitat they can rebuild their populations. The impacts on the population were noticed in the 1950s, and with efforts in place there were approximately 1000 males accounted from by 1961, however, by 1971 that number declined to 400 (U.S. Fish & Wildlife Services). As we looked at the habitat of this species we can see that the issue at hand is their inability to adjust to environmental stochasticity and their loss of evolutionary flexibility. The habitat of the area that they occupy simply outgrows them. As the trees age the lower branches die off, and the new growth is unable to support the nests. Compounded by the cowbird as the breed is thriving and reproducing at a cost to the Kirtland Warbler, they can begin to take over the nest and push out the offspring and increasing