Are avian predators effective biological control agents for rodent pest management in agricultural systems

Steadman, David W. Holocene Vertebrate Fossils from Isla Floreana, Galapagos. Smithsonian Contributions to Zoology, number 413, 103 pages, 25 figures, 4 plates, 12 tables, 1986.—This study surveys the late Holocene vertebrate fossil record from Isla Floreana, Galapagos. Over 20,000 fossils from four lava tubes in the arid lowlands near Post Office Bay are associated with six radiocarbon dates of 2400 years B.P. or younger. The fossils, most of which originated as regurgitated pellets of barn owls, represent more than 1100 individual animals of 24 indigenous species. They include six species now extinct on Floreana: Geochelone elephantopus (tortoise), Alsophis biserialis (snake), Tyto punctatissima (Galapagos Barn Owl), Mimus trifasciatus (Floreana Mockingbird), Geospiza nebulosa (Sharp-beaked Ground Finch), and Geospiza magnirostris (Large Ground Finch). These species are, respectively, 1 st, 7th, 16th, 6th, 15th, and 2nd in abundance among all species recorded as fossils, making up 57% of the individuals in the fossil fauna. In addition, the 3rd and 4th most common fossil taxa, Tropidurus grayii (lava lizard) and Zenaida galapaf oensis (Galapagos Dove), are extremely rare today on Floreana. Thus, extinction probably ias changed the composition of Floreana's fauna even more than is suggested by the number of extinct species alone. While the e\idence is circumstantial, I believe that all extinction on Floreana is related to human impact, directly through predation and habitat alteration, and indirectly through the effects or alien animals (rats, mice, cats, dogs, pigs, goats, cattle, and donkeys). People and feral mammals have lived on Floreana since 1832, and most or all vertebrate extinction occurred within the succeeding 40-50 years. Direct predation by man and introduced mammals was probably the main cause of extinction only for Geochelone elephantopus, although such predation may have been involved to some extent in each of the other extinctions. Loss of preferred prey species and human predation probably caused the extinction of Tyto punctatissima. Extinction of Mimus trifasciatus and Geospiza magnirostris may have resuftea from destruction of Opuntia cactus by feral herbivores. Extinction of Geospiza nebulosa may be related to habitat changes in the highlands. Buteo galapagoensis (Galapagos Hawk), though not recorded as a fossil, is also apparently extinct on Floreana, with direct human predation likely to be the main cause. All extinction on Floreana occurred in historic times; whether this is true elsewhere in the Galapagos awaits more research. Lasiurus borealis (Red Bat) is the only indigenous mammal recorded as a fossil. The absence of fossils of cricetine rodents or Conolophus spp. (Land Iguana) is evidence that these forms never occurred on Floreana. The lack of fossils of Coccyzus melacoryphus (Dark-billed Cuckoo) and Dendroica petechia (Yellow Warbler), which occur commonly on Floreana today, is evidence that these two species colonized the Galapagos very recently. Fossil records depend upon suitable environments of deposition. The Galapagos Islands, being of recent volcanic origin, lack many potentially fossiliferous geological features such as fine-grained alluvial sediments, indurated sand dunes, or limestone caves and sinkholes. Fortunately, lava tubes, which are very well suited for accumulation and preservation of vertebrate fossils, are common on certain islands in the Galapagos. Fossils enable us to reconstruct undisturbed (pre-human) insular faunas more completely than previously possible. Modern biogeographical studies usually do not consider now natural the faunas are; they would benefit by considering changes wrought by human impact. The field of island biogeography woula profit from a renewed emphasis on the collection of original field data rather than the current trend of theoretical studies that often are based upon inadequate or poorly understood data. OFFICIAL PUBLICATION DATE is handstamped in a limited number of initial copies and is recorded in the Institution's annual report, Smithsonian Year. SERIES COVER DESIGN: The coral Montastrea cavernosa (Linnaeus). Library of Congress Cataloging in Publication Data Steadman, David W. Holocene vertebrate fossils from Isla Floreana, Galapagos. (Smithsonian contributions to zoology ; no. 413) Bibliography: p. Supt. of Docs, no.: SI 1.27:413 1. Vertebrates, Fossil. 2. Paleontology—Recent. 3. Paleontology—Galapagos Islands— Santa Maria Island. I. Title. II. Series. QL1.S54 no. 413 [QE881] 591 s [566] 85-600002

Holocene vertebrate fossils from Isla Floreana, Galápagos

Donnees sur la relative inefficacite predatrice de 3 especes de predateurs susceptibles de provoquer l'autotomie de la queue de 3 especes de d'Iguanidae en condition experimentale et sur la relative capacite de fuite de ces 3 especes de Liolaemus

http://www.jstor.org/stable/pdfplus/3565531.pdf

Experimental evidence that high population frequencies of lizard tail autotomy indicate inefficient predation

Food niches of Common Barn-Owl (Tyto alba) populations were studied for 8 years in Utah and Idaho. Small mammals dominated the diet as they do in most parts of the barn-owl's range. Mean prey weight was nearly identical between the two owl populations. Food-niche breadth, though, was significantly broader in Idaho than in Utah. Food-niche breadth was also more variable in Idaho than in Utah both within and between years. Voles (Microtus spp.) were predominant prey for both owl populations and were the only prey whose numeric variation in the diet significantly affected mean prey weight and food-niche breadth. Vegetative composition was less varied and more uniformly favorable to voles in Utah. The Idaho area contained a smaller poportion of good vole habitat but had a greater diversity of vegetation including deserts suitable for small mammal species not found in the Utah study area. These vegetative differences and their effects on small mammal species diversity and density were the most apparent causes ...

A Long-Term Study of Food-Niche Dynamics in the Common Barn-Owl: Comparisons within and Between Populations

Venomous bites by nonvenomous snakes: an annotated bibliography of colubrid envenomation

We show that the Mediterranean habitats of Chile, Spain and California are characterized by similar size distributions of small mammal species available to raptors, and that these prey resources are exploited by taxonomically related assemblages of owl species that exhibit similar distributions of body size. Barn owls (Tyto alba) in the three mediterranean areas are similar in that they take almost every small mammal species present. However, Spanish barn owls differ from those in Chile and California in that they take significant amounts of insects, amphibians and reptiles, and also in that the mean size of mammalian prey in their diet is considerably smaller than that for Chilean and California barn owls. These features are attributed to the reduced abundance of larger-sized small mammals in Spain, which presumably forces the barn owls to prey more heavily on the smallest mammals available and also on low-reward nonmammalian prey. The trophic parameters of barn owls in a Colorado grassland fall well within the range of variation exhibited by mediterranean barn owls and this is, associated with size distributions of mammalian prey and of syntopic owls which are similar between the two habitat types. The essential features determining the predation pattern of the barn owl in different parts of its range seem to be the statistical distribution of mammalian prey sizes available, the relative abundance of these prey and the configuration of the assemblage of syntopic owls.

https://www.jstor.org/stable/pdfplus/2425196.pdf

Predation by the Barn Owl (Tyto alba) in Mediterranean Habitats of Chile, Spain and California: A Comparative Approach

Pradation on reptiles at three Mediterranean-type habitat sites was assessed by computing the incidence of reptiles as a percentage of vertebrates in the diet of each predator species and the incidence of each reptile species as prey for the entire assemblage of predators at each locality The overall importance of reptiles is lowest in Chile, intermediate in California, and highest in Spain These differences do not appear to result from interlocality variation in the size distributions of predators or of prey The incidence of particular reptile species as prey is correlated with their relative abundances in Spain and California, but not in Chile Behavioral and morphological attributes evidently make some species more vulnerable to predation and others less so than their abundances would predict Predation on the speciose lizard genus Liolaemus in Chile is sufficient to promote behavioral responses but not major morphological divergence

Predation upon reptiles in Mediterranean habitats of Chile, Spain and California: A comparative analysis.

Human envenomation from the bite of an agluphous false coral snake, Pliocercus elapoides (Serpentes: Colubridae).

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Predation by the Barn Owl (Tyto alba) in Mediterranean Habitats of Chile, Spain and California: A Comparative Approach

Predation upon reptiles in Mediterranean habitats of Chile, Spain and California: A comparative analysis.

Human envenomation from the bite of an agluphous false coral snake, Pliocercus elapoides (Serpentes: Colubridae).