Age-related differences in diet and foraging behavior of the critically endangered Mariana Crow (Corvus kubaryi), with notes on the predation of Coenobita hermit crabs

Faegre, Sarah K.; Nietmann, Lindsey; Hannon, Phillip; Ha, James C.; Ha, Renee Robinette

doi:10.1007/s10336-019-01705-3

Cited by 9 publications

(10 citation statements)

References 45 publications

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“…These species were selected because they are moderately common on all four islands and produce adequate fruit crops for experiments. In over 100 h of fruiting tree observations and observations of foraging Mariana crows22, we observed all five avian frugivore species formerly found on Guam visiting these two tree species on Saipan and Rota (Fig. 1).…”

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confidence: 83%

Effects of an invasive predator cascade to plants via mutualism disruption

et al. 2017

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Invasive vertebrate predators are directly responsible for the extinction or decline of many vertebrate species, but their indirect impacts often go unmeasured, potentially leading to an underestimation of their full impact. When invasives extirpate functionally important mutualists, dependent species are likely to be affected as well. Here, we show that the invasive brown treesnake, directly responsible for the extirpation of forest birds from the island of Guam, is also indirectly responsible for a severe decline in plant recruitment as a result of disrupting the fruit-frugivore mutualism. To assess the impact of frugivore loss on plants, we compare seed dispersal and recruitment of two fleshy-fruited tree species on Guam and three nearby islands with intact disperser communities. We conservatively estimate that the loss of frugivorous birds caused by the brown treesnake may have caused a 61–92% decline in seedling recruitment. This case study highlights the potential for predator invasions to cause indirect, pervasive and easily overlooked interaction cascades.

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confidence: 83%

Effects of an invasive predator cascade to plants via mutualism disruption

et al. 2017

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“…Social aggregation of non-breeding individuals may be advantageous in habitats with defendable, patchy resources (Heinrich 1988, 2014). In contrast, the frequency of space use is not related to prey availability within home ranges of Mariana Crow family groups (Faegre 2017). Since Mariana Crows forage primarily on widely occurring insects and small animal prey (Jenkins 1983, Tomback 1986, Faegre 2017), it may be less advantageous to compete directly with conspecifics for food.…”

Section: Discussionmentioning

confidence: 88%

“…In contrast, the frequency of space use is not related to prey availability within home ranges of Mariana Crow family groups (Faegre 2017). Since Mariana Crows forage primarily on widely occurring insects and small animal prey (Jenkins 1983, Tomback 1986, Faegre 2017), it may be less advantageous to compete directly with conspecifics for food. Indeed, sub-adult Mariana Crows were most often observed foraging and roosting alone and they vocalised infrequently when conspecifics were nearby (R. Ha unpubl.…”

Section: Discussionmentioning

confidence: 88%

“…We recommend future study of spatial and temporal variation in juvenile mortality risk, combined with evaluation of whether trapping in the nest area has a detectable effect on the overall feral cat population in crow habitat. Ultimately, high first year mortality (Ha et al 2010), much of which occurs 6–12 months post-fledging (Faegre 2017) suggests that larger scale protection measures beyond predator control in nest areas may be necessary to address some of the principal threats to species recovery.…”

Section: Management Implicationsmentioning

confidence: 99%

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Spatial ecology of the Mariana Crow Corvus kubaryi: Implications for management strategies

Faegre

Nietmann

Hubl

et al. 2018

Bird Conservation International

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SummaryKnowledge of species-specific spatial ecology is critical for applying appropriate management strategies to maximise conservation outcomes. We used radio-telemetry to describe spatial behaviour of the critically endangered, island-endemic Mariana Crow Corvus kubaryi. To determine whether management strategies should reflect life stage, we measured the home ranges and daily movements of 22 Mariana Crows. Fledgling mobility was low during the first 31 days post-fledging and effects of age (fledgling or sub-adult) and time (months post-fledging or post-dispersal) were often driven entirely by this period. After controlling for reduced fledgling mobility, cumulative home range size increased over time for both age classes and was, on average, more than twice the area for sub-adults than fledglings. Sub-adults also tended to make longer daily movements than fledglings. Non-cumulative, monthly home range areas did not increase over time but the average overlap in home range area between consecutive months was only 63%, suggesting large shifts in space use each month. These results highlight the dynamic nature of Mariana Crow home ranges and suggest that large-scale management efforts are critical for protecting both breeding and non-breeding individuals. The application of the traditional home range concept to Mariana Crows and other wide-ranging passerine birds may result in sub-optimal management strategies. Instead, we recommend that the spatial and temporal scale of conservation efforts be informed by species-specific spatial behaviour across all relevant life stages.

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“…Given the cur rent level of available funds, we suggest that application of uniform islandwide hunting effort may not be the optimal strategy to maximize crow protection; rather, we suggest a multifaceted, targeted approach focused on areas of high crow activity. telemetry suggests that feral cats are con tributing to the decline of the Rota popula tion (Faegre 2015). Feral cats are known to be the cause of mortality for both adults and juveniles, and it is strongly recommended that feral cat control be integrated into the crow conservation program on Rota (Zarones et al 2015).…”

Section: Modeling Impacts Of Hunting On Control Of An Insular Feralmentioning

confidence: 99%