Lanius

Abstract: Ornithologists commonly estimate nest survival using the Mayfield method, which produces relatively unbiased estimates provided that key assumptions are met. However, this method cannot statistically model nest failure in relation to quantitative variables, nor can it consider the joint effects of two or more independent variables. We demonstrate the use of an alternative method, survival time analysis. Survival time analysis can incorporate nests that are found at different points in the nesting cycle and nests whose ultimate outcome is unknown. The method allows one to examine variation in nest mortality during the course of the nesting period. To demonstrate this method we analyze data on Loggerhead Shrike (Lanius ludovicianus) nests, collected as part of a 3-year monitoring program of shrubsteppe habitat in north-central Oregon. We evaluate nesting success with respect to laying date, nest height, and annual variation in failure rate. We demonstrate three types of analyses: Kaplan-Meier estim...

Abstract: Innovative behaviours are defined as new behaviour patterns derived by the modification of pre-existing ones. To date, studies of animal innovation have focussed mainly on foraging activity. In this paper, we focussed on the innovative use of a new material—man-made plastic (polypropylene) string—in nest construction by a solitary nesting, territorial species, the Great Grey Shrike Lanius excubitor. An analysis of field data collected during the years 1999–2006 during intensive shrike research in Poland, as well as of nest record cards since 1964, suggests that plastic string has been a very popular nest material since the 1980s. Recently, plastic string was used significantly more often by shrikes living in intensive farmland habitats than by those in more natural meadows. We discuss the possible benefits of the use of plastic string, such as strengthening the nest structure and therefore helping to protect eggs and nestlings from inclement weather conditions, such as strong winds. On the other hand, the use of plastic string has a real cost for breeding Great Grey Shrikes because both adult birds and nestlings may get tangled in it.

Abstract: Summary Indirect seed dispersal in the system Lycium intricatum (Solanaceae)–lizards (Gallotia atlantica)–shrikes (Lanius excubitor) was studied in Alegranza, a xerophytic small island of the Canarian archipelago. A total of 835 seeds (224 obtained from lizard droppings and 611 from shrike pellets) was found by analysing 123 droppings and 146 pellets. Lycium fruit remains (including seeds) were observed in 31.7% of the lizard droppings and 50% of the shrike pellets. As would be expected for legitimate seed dispersers, external seed damage produced by each species was negligible. Lycium seeds were significantly matched with the presence of lizard remains in shrike pellets. Seeds in shrike pellets have come from fruit consumed by lizards that have been predated by the shrikes, and not directly from bird frugivory. Seeds from shrike pellets showed significantly higher germination rates than those from uneaten fruits and lizard droppings. It seems probable that different treatments in the guts of each species and retention time are two main factors influencing the germination process. While gut pass time in G. atlantica has been estimated to be 2.42 days on average, the retention time of a seed inside a shrike gizzard is much shorter (45–55 min). This is a new case of the scarcely known phenomenon of indirect seed dispersal, which seems to acquire a relatively important role in small islands where the animal–plant interaction is very intense and all the elements of the system are native.

Abstract: We report the presence of a 128 bp tandem repeat in the mitochondrial control region of the loggerhead shrike (Aves: Lanius ludovicianus) All individuals examined had either two or three copies of the repeat or were heteroplasmic for two and three copies This is the first direct demonstration of a tandem repeat associated with heteroplasmy in the control region of a bird A novel model for repeat duplication, which involves an inverted repeat located adjacent to the tandemly repeated sequence, is presented Individuals with three repeats are absent from the endangered population of San Clemente loggerhead shrike in southern California, suggesting that the island endemic has a small effective population size and that there is insignificant gene flow from the adjacent mainland