Demographic negative effects of diverse migration actions analyzed within the a great metapopulation off tundra swans

Demographic negative effects of diverse migration actions analyzed within the a great metapopulation off tundra swans

Migration was popular aspect of the lifestyle reputation for of several avian types, but the demographic consequences away from variable migration strategies have only infrequently started investigated, and rarely while using progressive technical and you can analytical tricks for examining success, direction designs, and you may a lot of time-title productivity relating to life background idea. I tracked the newest fates off fifty satellite-implanted tundra swans (Cygnus columbianus) more than 4 age out-of four different reproduction elements inside the Alaska, and you can used recognized-destiny analyses in order to redirected here guess monthly emergency likelihood prior to migration point, breeding town, migratory flyway, breeding position, and you can decades. I especially checked out whether migratory wild birds deal with a swap-from, by which enough time-point migrants see highest endurance cost at the cost of straight down yields because of smaller big date towards reproduction areas according to birds you to definitely migrate less distances and you can save money big date on the breeding parts.

Results

Yearly migration distances ranged significantly certainly breeding elements (1020 so you’re able to 12720 km), and you can had been strongly adversely correlated eventually spent on reproduction components (roentgen = ?0.986). Quotes from yearly endurance opportunities varied because of the wintering city (Pacific coastline, Alaska Peninsula, and Eastern seaboard) and you may varied of 0.79 (95%CI: 0.70–0.88) to 1.0, dependent on requirements familiar with discern mortalities out-of radio downfalls. I did not discover evidence for an excellent linear relationship between migration length and you can success since swans on the breeding parts towards the shortest and longest migration ranges had the higher emergency likelihood. Endurance is actually lower in the initial year article-establishing than in then ages, however, there’s not support for regular variations in emergency. Returns ranged among breeding populations and you will was essentially inversely coordinated to help you endurance, although not migration distance or date spent on reproduction areas.

Results

Tundra swans agreed so you can a primary tenet regarding lives history principle, just like the populations toward large emergency basically met with the lower production. Having less an effective uniform matchmaking anywhere between go out allocated to breeding parts and efficiency, otherwise time spent on wintering portion and you will endurance, shows that circumstances aside from temporary capital influence group effects during the so it variety. The latest tremendous diversity of migration methods we pick inside the Alaskan tundra swans, in place of clear impacts towards success, underscores the ability of which variety so you’re able to adapt to additional surroundings and you may climatic regimes.

Background

Migration are a behavioral characteristic that is thought to has actually evolved to maximise fitness from inside the regular environment, that’s a favorite facet of the lifestyle reputation of of a lot avian types [1–4]. Understanding the group consequences regarding migration is definitely a goal out-of avian ecologists, once the pinpointing the new physical fitness costs associated with some other behaviours is to further our knowledge of systems riding the latest evolution and you can restoration of avian existence history tips [5, 6]. To have snowy-breeding wild birds undergoing extended biannual migrations, the expenses of these an electrical energy demanding conduct may be substantial in terms of each other breeding and you may success Array.

The ability price of a lot of time migrations is let me make it clear higher having probably higher negative affects on breeding, because migrants need certainly to balance ranging from having fun with energy having airline and you will storing supplies to have reproduction [9, 10]. Particularly prices are more than likely best when you look at the pure resource breeders, you to instead of income breeders, cannot offset the active weight out-of migration because of the foraging toward breeding components. The price of migration, particularly much time-length migration, into the emergency was faster obvious but of interest, because the population dynamics out-of enough time-stayed kinds are according to adult endurance [eleven, 12].

There are numerous contending hypotheses about the market effects out of long distance migration. Many experts enjoys contended you to enough time migrations must specific a toll in terms of smaller survival than the inactive species [eight, 13], and contains been proven you to definitely birds holding a lot more times supplies (meaning that capable of traveling further) are more vulnerable to predation than just leaner birds [3, 14]. Birds with expanded migrations may also experience improved mortality as they cross an increased range away from terrain and are and this potentially unwrapped to help you a much bigger package of predators than simply sedentary variety. Alternatively, anyone else enjoys debated you to wild birds move to help you places where mortality is actually quicker, and they are ergo likely to have highest endurance prices than simply citizen kinds otherwise kinds you to definitely traveling quicker much [15–18]. In fact, Greenberg recommended you to definitely migratory wild birds deal with a trade-out of, wherein enough time-length migrants understand large endurance prices because they travelling after that so you’re able to visited so much more ordinary wintering portion, but at the expense of straight down productivity because of using concomitantly less time toward reproduction elements [fifteen, 19]. The guy termed so it dichotomy out of capital new “Go out Allowance” theory hence predicts you to definitely, inside migratory birds, returns and you will emergency is determined from the temporary financial support, having people increase in length of new breeding 12 months causing good ount of energy to possess consuming the fresh new low-reproduction assortment. As such, you to forecast would be the fact populations in the higher latitudes, having much time migration ranges, must have high endurance rates and lower efficiency than simply residents otherwise short-range migrants [fifteen, 20]. Several research has tested predictions of time allotment theory having varying abilities (come across critiques inside the [19, 21, 22]).

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