Determining the impact of forest disturbance and fragmentation on tropical biotas is a central goal of conservation biology. Among tropical forest birds, understory insectivores are particularly sensitive to habitat disturbance and fragmentation, despite their relatively small sizes and freedom from hunting pressure. Why these birds are especially vulnerable to fragmentation is not known. Our data indicate that the best determinant of the persistence of understory insectivorous birds in small fragments is the ability to disperse through deforested countryside habitats. This finding contradicts our initial hypothesis that the decline of insectivorous birds in forest fragments is caused by impoverished invertebrate prey base in fragments. Although we observed significantly fewer insectivorous birds in smaller fragments, extensive sampling of invertebrate communities (106,082 individuals) and avian diets (of 735 birds) revealed no important differences between large and small fragments. Neither habitat specificity nor drier fragment microclimates seemed critical. Bird species that were less affected by forest fragmentation were, in general, those that used the deforested countryside more, and we suggest that the key to their conservation will be found there. F orest understory insectivores, in general, have high habitat specificity, low mobility, and are more confined to forest interior than other forest passerine guilds, especially in the tropics where forest fragmentation and its consequences are most dramatic (1-5). Although over a dozen hypotheses have been proposed to explain the disappearance of insectivorous bird species from forested habitats around the world (2, 6), four of these are particularly relevant to explaining the decline of understory insectivores. The food scarcity hypothesis states that small fragments are impoverished in prey preferred by understory insectivores (6-8). The microclimate hypothesis proposes that these birds are particularly sensitive physiologically to changes in microclimate associated with forest fragmentation (2, 9). The habitat specificity hypothesis states that the loss of some microhabitat elements (such as army ant swarms, curled leaves, and dead trees) from fragments may affect many understory insectivores negatively (2, 6). Insectivores are more sensitive to such subtle changes because, unlike fruits, flowers, and seeds, invertebrates actively avoid insectivores and, as a result, insectivorous birds have evolved into many specialized niches and seek prey in certain microhabitats. Finally, according to the limited dispersal hypothesis, understory insectivores, because of their relatively sedentary habits and possible psychological avoidance of clearings (1, 10), may be less likely to disperse into more favorable habitats after forest fragmentation and may disappear from fragments as a result of stochastic events and other negative consequences of fragmentation.Changes in invertebrate communities as a result of forest fragmentation are well documented (11-13). Leaf-litter...

We address criticism that the Transport, Establishment, Abundance, Spread, Impact (TEASI) framework does not facilitate objective mapping of risk assessment methods nor defines best practice. We explain why TEASI is appropriate for mapping, despite inherent challenges, and how TEASI offers considerations for best practices, rather than suggesting one best practice. Our review of alien species risk assessments (RA) (Leung et al. 2012) aimed to synthesise the diverse approaches applied in this field to establish a logical framework for best practices. We believe the TEASI framework that makes explicit the consideration of Transport, Establishment, Abundance, Spread and Impact aspects of biological invasions helps integrate the main ideas underlying risk assessment and identifies important open questions. Barry (2013) provided a thoughtful review of our study and while he found much to commend in our approach, he indicated two main criticisms: (1) the mapping process in the article was subjective and TEASI does not encapsulate all the reviewed RAs and (2) we are not explicit in defining the best practice. We address each criticism. First, although quantitative approaches were relatively easy to map onto the TEASI framework, scoring-based approaches were more difficult and more subjective. Importantly, subjective does not mean arbitrary. For instance, mapping RA questions such as 'propa-gules dispersed by wind' onto the Spread component in TEASI and identifying it as a species trait is arguably logical. However, the rationale for how answers were combined was less clear for scoring approaches. For instance, many simply summed binary yes/no answers across all components, so we agree that they 'would need to be radically redefined' to map onto TEASI as many do not consider model structure. Barry (2013) further notes that the scoring approaches 'are abstract while the TEASI model is process-based and explicit'. This is certainly true but if the 'abstract' risks do not (at least imperfectly) map onto the set of real processes underlying invasions, we question whether they can be predictive. Thus, we argue that scoring-based approaches can and should be considered in the context of a process-based framework, but we acknowledge that this is challenging. We view this difficulty in mapping model structure as a limitation of existing scoring methodology rather than of the process-based TEASI model. We pose the questions: do the scoring model structures make sense in terms of invasion processes? How? If they do not, in the future, should they? Note, we do not deny the value of scoring RAs; they will remain important in addressing biological invasions, given limited time, data and resources. In addition, Barry (2013) argues that TEASI equations were too highly structured and prescriptive. Although we could have just listed factors thought to be relevant for invasion risk, this would be less valuable. Models are useful, in part, exactly because they are highly structured, presenting a clear picture of how we believe factors rel...