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Manipulated density of adult mallards affects nest survival differently in different landscapes
Kristianstad University, Department of Mathematics and Science. (Akvatisk biologi och kemi)
Kristianstad University, Department of Mathematics and Science. (Akvatisk biologi och kemi)ORCID iD: 0000-0003-2345-3953
2007 (English)In: Canadian Journal of Zoology, ISSN 0008-4301, E-ISSN 1480-3283, Vol. 85, no 5, 589-595 p.Article in journal (Refereed) Published
Abstract [en]

Breeding success in many birds including wildfowl is mainly determined by nest predation. Few studies address cues used by predators to find duck nests, and the same is true for spacing patterns that ducks might use to reduce predation. We designed a crossover experiment in agricultural and forested settings to test the assumption that nest predation rate is related to density of adult birds on a lake. We used introduced wing-clipped mallards (Anas platyrhynchos L., 1758) to increase local pair density and semi-natural nests to assess predation rate. Depredation patterns were analyzed by model fitting in program MARK, using introduction and landscape type as main effects and abundance of avian predators and wild waterbirds as covariates. Depredation was higher at agricultural lakes than at forest lakes. Nest survival decreased with increasing abundance of wild waterfowl, whereas it tended to increase with the abundance of "other waterbirds". There was a landscape-dependent effect of increased mallard pair density: positive at agricultural lakes and negative at forest lakes. Avian predators found 91% of depredated "known-predator" nests at agricultural lakes and 25% at forest lakes; mammals found 9% at agricultural lakes and 75% at forest lakes. The landscape-dependent density effect may in part be due to different predator communities in these landscape types.

Place, publisher, year, edition, pages
2007. Vol. 85, no 5, 589-595 p.
Keyword [en]
ARTIFICIAL DUCK NESTS, PREDATION RISK, HABITAT SELECTION, TEMPORAL, PATTERNS, WATERFOWL NESTS, CROW PREDATION, REAL NESTS, SUCCESS, PARASITISM, DYNAMICS
National Category
Biological Sciences
Identifiers
URN: urn:nbn:se:hkr:diva-196DOI: 10.1139/Z07-038ISI: 000248223600001ISBN: 0008-4301 (print)OAI: oai:DiVA.org:hkr-196DiVA: diva2:173902
Available from: 2009-02-18 Created: 2009-02-11 Last updated: 2014-06-05Bibliographically approved
In thesis
1. Survival patterns and density-dependent processes in breeding mallards Anas platyrhynchos
Open this publication in new window or tab >>Survival patterns and density-dependent processes in breeding mallards Anas platyrhynchos
2007 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Measuring and assessing vital rates such as births and deaths are prerequisites for understanding population dynamics. Vital rates may be affected by the density of individuals, even though the importance of density dependence on population dynamics has been debated for a long time. The mallard Anas platyrhynchos is one of the foremost game species in the Holarctic, with millions of birds in hunters’ bags annually. Still, basic knowledge about regulation of mallards’ vital rates is poor, and experimental studies on this topic are rare.

In this thesis I have studied survival patterns and density dependence in mallards breeding in Sweden and Finland. Long-term ringing data from both countries were analysed for mortality patterns and causation, as well as for e.g. survival rate estimation. Most of the studies were, though, experiments run over two years involving manipulations of the density of nests, broods and/or adults, in southern and northern Sweden, comprising different biotic regions. Common response variables were survival of nests, ducklings and hens, mainly analysed with program MARK.

About 90% of the recovered mallards in Finland and Sweden were hunting kills. However, survival rates were high, ranging from 0.66 to 0.81 for most groups (sex*age). The generality of density dependence was evident since such processes were detected in all studies. Consequently, depredation rate was higher in high nest density compared to low nest density. Survival of ducklings was density-dependent in both boreal and nemoral biotic regions, with food limitation being evident in the former region but not in the latter. In spite of their generality, density-dependent patterns varied within as well between years, and for nest predation rates also between landscape types.

The findings about density dependence in breeding mallards in this thesis are novel since they are based on experiments. They are potentially of general interest for management because they embrace a variety of lakes in two geographically distant areas, each being representative for large temperate areas in the northern hemisphere. Detection of density dependence at the local scale may be important at larger scales, too, following the principle of ‘ideal preemptive distribution’ in a source-sink dynamic system.

Place, publisher, year, edition, pages
Umeå: Department of Wildlife, Fish, and Environmental Studies, Swedish University of Agricultural Sciences, 2007. 39 p.
Series
Acta Universitatis agriculturae Sueciae, ISSN 1652-6880 ; 2007:12
Keyword
broods, dabbling ducks, density dependence, ducklings, experiments, models, mortality, nest predation, regulation, survival
National Category
Ecology
Identifiers
urn:nbn:se:hkr:diva-6782 (URN)978-91-576-7311-4 (ISBN)
Public defence
2007-03-23, Sveriges Lantbruksuniversitet, Alnarp, 09:00 (English)
Opponent
Supervisors
Available from: 2010-08-24 Created: 2010-06-28 Last updated: 2014-06-05Bibliographically approved

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