Re‐establishing the pecking order: Niche models reliably predict suitable habitats for the reintroduction of red‐billed oxpeckers

Abstract

Distributions of avian mutualists are affected by changes in biotic interactions and environmental conditions driven directly/indirectly by human actions. The range contraction of red‐billed oxpeckers (Buphagus erythrorhynchus) in South Africa is partly a result of the widespread use of acaracides (i.e., mainly cattle dips), toxic to both ticks and oxpeckers. We predicted the habitat suitability of red‐billed oxpeckers in South Africa using ensemble models to assist the ongoing reintroduction efforts and to identify new reintroduction sites for population recovery. The distribution of red‐billed oxpeckers was influenced by moderate to high tree cover, woodland habitats, and starling density (a proxy for cavity‐nesting birds) with regard to nest‐site characteristics. Consumable resources (host and tick density), bioclimate, surface water body density, and proximity to protected areas were other influential predictors. Our models estimated 42,576.88–98,506.98 km2 of highly suitable habitat (0.5–1) covering the majority of Limpopo, Mpumalanga, North West, a substantial portion of northern KwaZulu‐Natal (KZN) and the Gauteng Province. Niche models reliably predicted suitable habitat in 40%–61% of the reintroduction sites where breeding is currently successful. Ensemble, boosted regression trees and generalized additive models predicted few suitable areas in the Eastern Cape and south of KZN that are part of the historic range. A few southern areas in the Northern Cape, outside the historic range, also had suitable sites predicted. Our models are a promising decision support tool for guiding reintroduction programs at macroscales. Apart from active reintroductions, conservation programs should encourage farmers and/or landowners to use oxpecker‐compatible agrochemicals and set up adequate nest boxes to facilitate the population recovery of the red‐billed oxpecker, particularly in human‐modified landscapes. To ensure long‐term conservation success, we suggest that the effect of anthropogenic threats on habitat distributions should be investigated prior to embarking on a reintroduction program, as the habitat in the historical range may no longer be viable for current bird populations.

Large mammal declines and the incipient loss of mammal-bird mutualisms in an African savanna ecosystem

“…Paleontological studies suggest that megafauna extinctions during the Late Pleistocene and early Holocene led to subsequent coextinction cascades of commensalistic bird species that were incapable of adaptive shifting [ 1 , 81 ]. Indeed, oxpeckers have undergone substantial range reductions and local extinctions in parts of South Africa, following the replacement of preferred large-bodied wild ungulate hosts with livestock [ 18 , 30 , 82 ]. Globally, large mammals have either gone locally extinct or have undergone substantial population declines [ 83 , 84 ], a pattern that is mirrored within protected areas in the Tarangire-Manyara ecosystem [ 51 , 52 ], and especially pronounced in areas with little or no protection [ 32 ].…”

Comparing pseudo-absences generation techniques in Boosted Regression Trees models for conservation purposes: A case study on amphibians in a protected area

“…Even though the use of AUC to evaluate discrimination performance of SDMs has been questioned [ 29 , 48 ], this metric is used in several recent papers, dealing with biodiversity conservation (e.g. [ 26 – 28 ]) or other research fields [ 49 , 50 ], even when the authors themselves state that the absence data they use may not reflect real absences [ 28 ]. We used AUC as discrimination metric for the BRT models obtained because, even though it should not be used to compare models for different species in presence-background models [ 29 ], it can still be used to compare different modelling approaches applied to the same species at the same extent [ 48 ], which is one of the main purposes of this paper.…”

“…Among them, Boosted Regression Trees (BRT) [ 15 , 16 ] is one of the modelling techniques most recently applied to conservation issues (e.g. [ 24 , 26 – 28 ]). BRT results from the combination of regression trees, which belong to the decision tree group of models, and boosting technique, which allows modellers to produce a large number of simple tree models and then combine them so as to optimize predictive potential [ 15 ].…”

Oxpeckers Help Rhinos Evade Humans

“…Thus, most rhino populations now exist without them. Conservationists might consider re-introducing oxpeckers to rhino populations [28] or re-introducing the two species simultaneously to wildlife reserves to reinstate a proven anti-human sentinel for rhino. Both are conservationreliant biodiversity [10,29] and oxpeckers might help improve rhino survival where park security fails to deter or detect illegal hunting [8].…”