Distinguishing regular timing off mortality within the migratory birds is additionally a beneficial trick believe, because rates from annual endurance, when you are of use, prevent attributing mortality so you’re able to a specific period of the annual duration and could restrict identity of situations probably regulating the populace. In one of the couple degree to hook success out of much time-distance migrants to seasonal time periods, Klaassen mais aussi al. tracked brand new migration of a lot types of raptors using satellite telemetry, and found one to morality costs was indeed actually high during attacks off migration.
Tundra swans (Cygnus columbianus) are highest migratory waterfowl you to breed in tundra environment throughout really of your Holarctic and you his comment is here will winter inside the north moderate climates at different degrees of latitude. The newest Us subspecies (C. c. columbianus) nests nearly continuously regarding the suggestion of Alaska Peninsula inside the south-west Alaska into the east side of Hudson Bay Canada, and also in asian Chukotka . Migration try a popular behavior from tundra swans, as they invest the year moving both to and from the breeding factor. Migration ranges and you can routes are different a lot more certainly usually disjunct wintering communities [27–29], enabling in depth research of market variables relative to adaptation inside migratory behaviour. Here, having fun with modern technical and analytical steps, we establish information about issues about the success from tundra swans inserted that have satellite transmitters that moved changeable ranges so you’re able to wintering websites off four different breeding elements round the their diversity into the Alaska. I fool around with a reports-theoretic method and recognized fate emergency quote to assess the fresh relative importance of facts almost certainly affecting brand new survival of swans, and additionally migration range, migratory flyway, years, and you will breeding success, whenever you are accounting for state (prevalence out of avian influenza worms and you will bloodstream parasites) and you can contaminants. I evaluate success quotes and you will breeding-area-certain indicator out of efficiency to assess possible change-offs between endurance and you may returns in the context of migration length and you can temporal financing.
Research species
Tundra swans (Cygnus columbianus) are considered good k-chose species as they provides put off breeding (do not reproduce up to about three-years old), and tend to be proven to alive more than 20 years in the open . Tundra swans was very based upon into the wetlands to own roosting and you may giving, but have also adjusted to feeding to your agricultural crops . In regards to our study, tundra swans was basically seized whenever flightless, within the annual side molt in at the four different breeding areas during the Alaska (Fig. 1). The latest intercourse out of birds is actually determined centered on cloacal services and you may inner examination. Birds were categorized to help you many years since possibly residents (we.elizabeth. cygnets), next seasons birds (SY; birds hatched the earlier season), or just after next seasons birds (ASY). Second 12 months birds was basically renowned regarding old wild birds of the visibility from grey feathering on the lead and shoulder, and frequently, back . Swans had been classified according to breeding status as often breeders (people that have cygnets), territorial pairs (people in place of cygnets towards the an area), otherwise non breeders (ASY otherwise SY wild birds inside communities). Satellite transmitters (platform providing terminals [PTTs]; model one hundred, one or two AA batteries [50 grams total mass], Microwave Telemetry, Columbia, MD); have been abdominally inserted for the 50 tundra swans (10 at each and every of five some other reproduction elements) in the range of brand new kinds during the Alaska. Transmitters had percutaneous antennas [32, 33] you to definitely exited the human body to own code fuel very important to satellite indication.
Place from satellite-, demonstrating first migration routes out-of five more reproduction portion. Fall and you may springtime migration routes is actually equivalent. Hatched polygons try wintering portion. Most Down Alaska Peninsula swans don’t move
Actions
PTTs was developed to send for five h after which turn out-of getting 72 h during summer and you may cold temperatures attacks, and be out-of getting 18 h throughout migration symptoms for the fall and springtime . The fresh PTTs was indeed built to aired for a couple of age; in case the 2-year several months are exceeded, the duty stage reverted so you’re able to 5 h with the and 72 h out-of into longevity of the fresh transmitter. The new Argos Analysis Collection and Venue Program was utilized to find information regarding latitude and longitude, date, go out, top-notch area, body temperature, and you can pastime from swans instrumented that have PTTs. Unrealistic locations had been filtered centered on rates and angle of motion in addition to highest quality locations were utilized to depict day-after-day position .
