Our very own prices out-of annual endurance for swans designated toward Lower Alaska Peninsula ranged away from 0

Our very own prices out-of annual endurance for swans designated toward Lower Alaska Peninsula ranged away from 0

93 to just one.0. This is certainly more higher than the brand new indicate visible yearly success imagine off 0.61 from inside the ages 1978–1989 getting neck-collared swans in one venue . Meixell mais aussi al. recommended the low and you will variable rates out-of visible yearly endurance to have LAP swans could have resulted from higher and varying rates away from long lasting emigration. Of your ten swans i designated towards LAP, only dos migrated out of Alaska during the winter, and you can one another anyone came back an identical 12 months. A leading proportion regarding neck banded swans on the LAP was basically identified with the wintering areas every year (C. unpubl. data), and this demonstrates heterogeneity from the migration tendencies out-of LAP swans, but it does not necessarily present them while the an unbarred society.

Highest annual endurance from inside the swans as the used in this study possess been recently detailed of the most other investigators. Into the a corner-types testing, Bart, Earnst and you will Bacon learned that migratory swan variety, together with tundra, Bewick’s (C. c. bewickii), whooper (C. cygnus), and you will trumpeter (C. buccinator), had highest yearly adult endurance pricing (close 90 %), than non-migratory adult swans, and additionally mute (C. olor), black colored (C. atratus), and you will black colored-necked (C. melanocoryphus) which got annual endurance costs out-of 80–85 %.

You can sourced elements of adaptation in the endurance

For systems of your own study found in quote of success the major models classified survival of the wintering location, forecasting you to swans with cold temperatures range along the Pacific shore had all the way down endurance as opposed to those you to definitely wintered into the east seaboard and you may the fresh seemingly sedentary swans about down Alaska Peninsula. There are many items regarding the fresh distribution regarding avian populations that will connect with survival . Hunter compile could limit communities off higher-bodied Anatidae and can even probably perception tundra swan communities, even if none of our own PTT-designated birds was claimed getting become gathered. This isn’t too stunning as federal and state/provincial providers basically restrict assemble regarding tundra swans compared to Cougar dating review almost every other waterfowl, as well as on mediocre dos = 0.97; Dining table step 1); the second, and its own mutual (weeks used on non-reproduction components) had been also maybe not predictive from endurance opportunities. As a result, tundra swan communities full don’t follow committed allotment hypothesis, about when it comes to factors affecting survival. There are many areas of the life span history of tundra swans which could help define why this is the scenario. Before on conversation i felt as to why variety one to migrate very slow, instance tundra swans, may possibly not be influenced by the brand new active cost of migration. The massive system measurements of tundra swans is yet another lives background characteristic you to sets her or him aside from many other variety; on account of thermoregulation factors regarding system bulk, tundra swans may not work for as much away from travel next in order to light wintering basis as faster passerines examined from the Greenberg . In fact, the brand new tundra swans society one to migrated the brand new furthest (CRD) didn’t wintertime within the a milder climate as compared to almost every other populations, because the mid-cold temperatures heat (January) inside the seaside New york (Nags Direct; 2.2 °C) is actually cooler compared to the Main Valley from California (Stockton; 3.step 3 °C) where KSL and you will YKD swans cold temperatures.

Ely ainsi que al

Even when Alaska-breeding tundra swans didn’t strictly comply with brand new forecasts of enough time allowance theory, there are patterns from inside the market details along side populations which might be worth listing, the most obvious where is actually the fresh new inverse matchmaking anywhere between success and you can production, with CRD and LAP swans with seemingly large survival and you may low yields than the YKD/KSL swans which in fact had relatively reduced emergency, however, high efficiency (Figs. cuatro and you can 5). This will be worth note, as in steady communities (hence this type of communities was [72, 73]), endurance and reproduction is actually regarding-mode , but empirical research support that it tenet from the people level are a bit uncommon. The lower production away from BBL swans, even after a comparatively lowest success price, is generally regarding large nest predation rates from the all the way down latitudes , saturated reproduction habitats causing an overabundance out of non-breeders, or even to other variables intrinsic towards Alaska Peninsula eg a high brownish happen [Ursus arctos] populace.

Leave a Reply

Your email address will not be published. Required fields are marked *