Does supplemental feeding affect the viability of translocated populations? The example of the hihi

Abstract

Translocations are commonly used conservation actions that aim at establishing new, self‐sustaining populations of threatened species. However, many translocated populations are not self‐sustaining but managed through supplemental feeding from the onset. Often, the decision to start managing is ad hoc, but managers will eventually have to make decisions for the future, for example, stop intervening, continue as it is or change the quantity of food provided. Such a decision requires managers to quantify the importance of supplemental feeding in determining the performance and population dynamics of translocated populations, information that is rarely available in the published literature. Using the hihi as a case study, we examined the importance of supplemental feeding for the viability of a translocated population in New Zealand. We found that supplemental feeding positively affected the survival and abundance of translocated adult hihi but also found evidence of negative density dependence on recruitment. We present two stochastic population models that project the hihi population under different management scenarios, quantitatively assessing the impact supplemental feeding has had on the population. Our results illustrate how important long‐term targeted monitoring is for robust decision making about adaptive management.

Targeted management buffers negative impacts of climate change on the hihi, a threatened New Zealand passerine

“…There were nine feeders, five of which were active all year round and located in the middle of the island, where the hihi population is restricted. During ad libitum feeding extensive amounts of sugar water was provided, peaking at an estimated 3638 l annually (Chauvenet et al, 2012).…”

“…Different strategies will have different costs, and one of the cheaper strategies is supplementary feeding (SF). The benefits of SF for threatened species are well-documented (although see (Clout et al, 2002) for a caution): SF provides safe food sources (Wilbur et al, 1974), improves vital rates (Elliott et al, 2001) and leads to increases in size of small populations (Cabezas and Moreno, 2007;Chauvenet et al, 2012). However, while SF is widespread (e.g.…”

“…It is a threatened endemic New Zealand passerine bird, which is restricted to small isolated populations in a highly fragmented landscape. Islandrestricted passerines, like the hihi, represent a useful system to examine the relationships between management interventions and climate due to their restricted range, annual reproduction, relatively easy capture and estimation of demographic parameters (Chauvenet et al, 2012). Moreover, hihi population dynamics are known to be influenced by climate conditions, with increases in temperature resulting in a predicted reduction in population size and increased extinction probability .…”

Maximizing the success of assisted colonizations

“…Unfortunately, translocated populations that are not subject to management actions, such as feeding or supplementation of individuals, at least for some years after translocation, are rare (see e.g. Chauvenet et al, 2012;Soorae, 2012), making this measure of success inadequate on the shorter term.…”

Food supplementation does not increase demographic rates in a passerine species of conservation concern

“…For example, in the New Zealand hihi, providing supplementary food increased abundance and survival of translocated birds on Kapiti Island, following evidence that food was limiting on previous island translocations (Chauvenet et al 2012). It is also important that the life-history stage(s) which are most likely to influence population growth rate (λ) of the study population are targeted for conservation action.…”