Author Correction: Arctic avian predators synchronise their spring migration with the northern progression of snowmelt.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Arctic avian predators synchronise their spring migration with the northern progression of snowmelt.

Migratory species display a range of migration patterns between irruptive (facultative) to regular (obligate), as a response to different predictability of resources. In the Arctic, snow directly influences resource availability. The causes and consequences of different migration patterns of migratory species as a response to the snow conditions remains however unexplored. Birds migrating to the Arctic are expected to follow the spring snowmelt to optimise their arrival time and select for snow-free areas to maximise prey encounter en-route. Based on large-scale movement data, we compared the migration patterns of three top predator species of the tundra in relation to the spatio-temporal dynamics of snow cover. The snowy owl, an irruptive migrant, the rough-legged buzzard, with an intermediary migration pattern, and the peregrine falcon as a regular migrant, all followed, as expected, the spring snowmelt during their migrations. However, the owl stayed ahead, the buzzard stayed on, and the falcon stayed behind the spatio-temporal peak in snowmelt. Although none of the species avoided snow-covered areas, they presumably used snow presence as a cue to time their arrival at their breeding grounds. We show the importance of environmental cues for species with different migration patterns.

A Video Surveillance System to Monitor Breeding Colonies of Common Terns (Sterna Hirundo).

Many waterbird populations have faced declines over the last century, including the common tern (Sterna hirundo), a waterbird species with a widespread breeding distribution, that has been recently listed as endangered in some habitats of its range. Waterbird monitoring programs exist to track populations through time; however, some of the more intensive approaches require entering colonies and can be disruptive to nesting populations. This paper describes a protocol that utilizes a minimally invasive surveillance system to continuously monitor common tern nesting behavior in typical ground-nesting colonies. The video monitoring system utilizes wireless cameras focused on individual nests as well as over the colony as a whole, and allows for observation without entering the colony. The video system is powered with several 12 V car batteries that are continuously recharged using solar panels. Footage is recorded using a digital video recorder (DVR) connected to a hard drive, which can be replaced when full. The DVR may be placed outside of the colony to reduce disturbance. In this study, 3,624 h of footage recorded over 63 days in weather conditions ranging from 12.8 °C to 35.0 °C produced 3,006 h (83%) of usable behavioral data. The types of data retrieved from the recorded video can vary; we used it to detect external disturbances and measure nesting behavior during incubation. Although the protocol detailed here was designed for ground-nesting waterbirds, the principal system could easily be modified to accommodate alternative scenarios, such as colonial arboreal nesting species, making it widely applicable to a variety of research needs.

Serum biochemistry values, plasma mineral levels, and whole blood heavy metal measurements in wild northern goshawks (Accipiter gentilis).

Serum chemistry panels and complete mineral and heavy metal screens were performed on blood samples from eight adult northern goshawks (Accipiter gentilis) breeding in Pennsylvania. Serum chemistry panels were performed to determine the health status of each bird. Biochemical values measured included serum glucose, sodium, potassium, chloride, magnesium, uric acid, creatine kinase, and aspartate transaminase. Glucose, creatine kinase, and aspartate transaminase values were elevated when compared with published values for northern goshawks and other species of raptors. Complete mineral screens were performed to better document the blood mineral content of northern goshawks. Plasma calcium, copper, iron, magnesium, total phosphorus, potassium, sodium, and zinc levels were determined. Whole blood heavy metal screens were done to evaluate the northern goshawk's exposure to environmental arsenic, cadmium, lead, thallium, and selenium. Arsenic, cadmium, lead, and thallium whole blood levels of less than 0.05 ppm in all birds indicated that the northern goshawks were not being exposed to significant levels of heavy metals in their environment. Whole blood selenium levels of the northern goshawks were above the minimum dietary requirement for avian species (0.130-0.200 ppm) and below published toxic selenium concentrations.