«1 ( student number: S1758675) Master thesis Animal Ecology & Evolution, Under supervision of: dr. M.J.J.E. Loonen 2 & Prof. dr. T. Piersma 1 1 Animal ...»
Effectivity of Dutch Goose management during the
J. van Eerbeek
Master thesis Animal Ecology & Evolution,
Under supervision of: dr. M.J.J.E. Loonen & Prof. dr. T. Piersma
Effectivity of Dutch Goose management during the
J. van Eerbeek 1 ( student number: S1758675)
Master thesis Animal Ecology & Evolution,
Under supervision of: dr. M.J.J.E. Loonen 2 & Prof. dr. T. Piersma 1
Animal Ecology Group, Centre for Lifesciences, University of Groningen, Nijenborgh 7, P.O. Box 11103 9700 CC Groningen, the Netherlands 2 Arctic centre, University of Groningen, A-weg 30, 9718 CW Groningen, The Netherlands
J. van Eerbeek, Vuurdoornstraat 36, 8924 AZ Leeuwarden, The Netherlands.
E-mail: J.van.Eerbeek@student.rug.nl Telephone: 0031-6-46388911 Colophon Text: J. van Eerbeek Lay-out: J. van Eerbeek Cover photo: Tok Poortvliet, hunting greylag geese. © Tok Poortvliet 2009.
Citation: van Eerbeek, J. (2013) Effectivity of Dutch Goose management during the breeding season. Master thesis Animal Ecology & Evolution, University of Groningen Index
Goose population development
Options for goose management
Scaring and disturbing
Removing, shaking and oiling of eggs
Present goose management
Discussion and conclusions
Opportunities to future research
Abstract The change in agricultural regimes and thereby the increased grass growth, combined with the demise in goose and fox hunting have caused the Netherlands to become a prime goose paradise. By extending their arctic breeding locations to more temperate latitudes such as the Dutch Delta the geese have increased their summer staging and breeding areas. Nowadays the Dutch goose population is the largest growing breeding bird population in Western Europe. As all growing wildlife populations the geese population causes conflicts with farmers who see their crop being consumed by all these geese. Crop damage is compensated by the government through the taxpayers. In this article we focus on the methods which can be used in goose management and their efficiency in population control. We provide different methods which can be used to control goose populations. Scaring techniques and biotope management are described. We show that goose reduction at the egg and juvenile stages has no impact on the population growth. Hunting is observed as a partly effective method but only when certain individuals are targeted. We perceive gassing to be efficient but only when the right portion to the population is culled. Finally we conclude that culling incubating females in the breeding colonies has an impact to retard the growth of the Dutch goose population.
Introduction Most of the Dutch Delta landscape is characterized by vast meadows of heavy intensified dairy and cattle farms. The fluctuating water levels of the rivers and the tidal influence of the sea together with the creeks, gullies and the extensive pastureland make the Dutch Delta a heterogenic safe haven for waterfowl and meadow birds in this highly intensified farming landscape.
Historically, growing populations of wildlife gave rise to conflicting interests with farmers in densely populated areas with highly intensified farming landscapes such as Western Europe.
Nowadays the fast growing portion of non migratory summer-staging and breeding geese in the Netherlands are a topic of debate because of the financial damage they cause to farmers which is compensated by the government through the taxpayers (Ouweneel, 2001; Voslamber et al., 2007; Voslamber & Turnhout, 2004).
The shift from extensive to intensive farming (Van Eerden et al., 2005), global warming (Hoglind et al., 2013), a reduction of hunting pressure by man (Ebbinge, 1991) and the intense eradication of foxes (Van der Jeugd et al., 2009; Voslamber et al., 2007) are main factors to the growing Dutch goose population. In 2005 there were 38.500 breeding pairs or
155.000 geese divided over 13 species (Van der Jeugd et al., 2006). Model predictions show that the greylag goose population will rise to 70.000 breeding pairs in 2017, the ceiling with
90.00 pairs will be reached around 2040 when all potential breeding grounds are colonized (Van der Jeugd et al., 2006). The canada goose and barnacle goose populations are rising quickly as well and will reach levels of 10.000 and 15.000-20.000 breeding pairs, but these levels are highly dependant on fox predation (Van der Jeugd et al., 2006).
Managing goose populations has proved to be quite difficult (Mooij, 1991) and populations are still expanding, both in number as in area of exploited farmland (Ebbinge et al., 2003;
Voslamber & Turnhout, 2004). Wintering geese which still migrate to the arctic breeding grounds are not seen as a problem by farmers because damage is small or non-existent (Van der Jeugd et al., 2009; Voslamber et al., 2007).
J. van Eerbeek, 2013 Effectivity of Dutch Goose management during the breeding season 2 In this article I give an overview of the methods used in Dutch goose management and the effects they might have on the summer staging non- migrating goose population. Summer staging geese are defined as wild geese, of any species, being present in the Netherlands in the period 1st April – 1st October (Faunafonds, 2008).
Density dependent effects are potential forces that can affect recruitment rate and population growth of nesting birds (Morrissette et al. 2010), their reproductive success appears strongly affected by food and nest site availability (Madsen et al., 2007) Habitat quality (McNab, 1963; Schoener, 1981; Ford, 1983; Mace et al., 1983) is a determining factor for home range size (Kilpatrick et al., 2001). The lower the competition within a group of organisms, and the better the habitat quality, the smaller the home range will be (Kilpatrick et al., 2001). Higher population densities assume better habitat quality (VanHorne, 1983) and animals living in better quality habitat need to travel less to obtain life requisites (Kilpatrick et al., 2001). Creating protected areas is an important part of the strategies for the conservation of species (Higgs, 1981; Margules & Pressey, 2000). However, in many animals, home range size exceeds protected area size (Kramer & Chapman, 1999;
Woodroffe & Ginsberg, 1999). In barnacle geese (Branta leucopsis) density dependent processes lead to carrying capacity, the competition for food on the breeding grounds causes gosling growth rate to be lower and gosling mortality to be higher (Loonen et al., 1997;
Larsson & Forslund, 1994). Even final adult body size was smaller when the adult was exposed to density dependant effects such as food competition as a gosling (Loonen et al., 1997; Larsson & Forslund, 1991).
In theory, when a habitat of good quality is exploited by many individuals of a particular species, and the saturation point of the carrying capacity is reached, intraspecific competition (Burt, 1943; Sanderson, 1966; Mace et al., 1983; Gese et al., 1989) will be strong and the area will “overflow” causing emigration to other, mostly lower quality, feeding areas (Cope et al., 2003). This is known as the buffer effect (Brown, 1969; Gill et al., 2001). As populations grow, an increasing portion of animals is displaced into poorer quality areas leading to reduced fecundity and survivorship (Gill et al., 2001).
Grazing by cattle causes sward canopy height to be lower and facilitates for the geese (Van der Graaf et al. 2002). Grazed areas are more preferred by the geese than the ungrazed nature reserves where the grass grows taller over the season (Van der Graaf et al. 2002). Goose grazing pressure is negatively correlated to canopy height which could be beneficial, by forcing geese into nomadic behaviour. This preference towards grazed pastures unfortunately increases the grazing damage inflicted to farmers. Contradictory, philopatry displayed by geese may cause them to stage in unsuitable habitats longer then one would expect (Rockwell et al., 1993), leaving the geese to breed in a slightly degraded habitat (Black & Owen, 1995).
When individuals are removed or culled from a population, intraspecific competition can be lower and therefore the production of offspring in next years can be larger. In fisheries biology, Maximum Sustainable Yield (MSY) is calculated annually, to optimize the harvest of pelagic fish stocks and to leave the remaining population in such a state that intra specific competition is quite low and next years recruitment will be optimal (Holmgren et al., 2012).
J. van Eerbeek, 2013 Effectivity of Dutch Goose management during the breeding season 3 Another good example for the importance of the concept of density dependence in wildlife management are red deer (Cervus elaphus) on hunting estates in Scotland.
When culled under 50 % of carrying capacity female red deer will give birth to male offspring more frequently (Clutton-Brock et al., 2002). Male deer are usually culled by fee-paying hunters making them beneficiary to the estates exchequer. By reducing female deer numbers Scottish deer managers also increase the food abundance for male deer making their antlers grow larger and making them an even more desirable trophy for hunters. This increases the managers annual take-off of mature males, and net income from deer management by the sale of female venison. Reduction of female deer numbers is likely to have benefits for tree regeneration which in turn will have further benefits to the deer population by an increase in forage and shelter (Clutton-Brock et al., 2002).
J. van Eerbeek, 2013 Effectivity of Dutch Goose management during the breeding season 4 Inclusive fitness Among species with overlapping generations, life- history theory predicts that survival and reproductive success are selected to maximize lifetime reproductive performance, thus fitness (Rockwell & Cooch, 1993). Inclusive fitness is basically the spread of genes of one female through a population. It can be true that as a breeding female from a long lived species, the female breeding next to you in a colony is your relative and holds the same genes as you do.
Altruism is encouraged in high genetic closeness and it would be better to slacken competition slightly in favour of your own offspring when it is breeding next to you (Taylor, 1992). As fitness is defined by a count of breeding offspring it seems reasonable for a mother or even grandmother not to compete with her daughter or granddaughter (Taylor, 1992).
When there is declining dispersal the relatedness of surrounding individuals rises and the more altruistic behaviour should be (Taylor, 1992). Limited dispersal leads to a correlation between maternal and offspring environments, which favours plastic adjustment of offspring size in response to local survival (Kuijper & Johnstone, 2013). In group-structured populations, altruistic acts can be selectively favoured only to the extent that an altruistic group is able to export a fraction of the benefits it generates (Grafen, 1983). Meaning that some of the additional offspring produced by this altruistic behaviour have to compete with individuals of relatively low relatedness (Taylor, 1992).
What counts is that the offspring can be accommodated by the environment in such a way that the offspring they would normally compete with do not feel the full effects of their presence.
This environmental elasticity is the only force which can mitigate the damping effect of local competition on the selective advantage of altruism toward relatives (Taylor, 1992). When the environment has no capacity for local expansion (inelastic), then selection pays attention to the direct effect of the actor on her own fitness, but not to her direct effects on any other individual, no matter how closely related that individual is (Taylor, 1992).
In semi structured populations, such as goose flocks, where family bonds can be observed, kin selection gives rise to more altruistic behaviour, such as lowering aggression towards kin and sounding alarm cries in a earlier stage to protect kin from approaching danger and predators (Van der Jeugd et al., 2002; Trivers, 1971). Settling close to kin with more altruistic behaviour can facilitate nest site acquisition and breeding success and herby raise inclusive fitness (Watson et al., 1994; Van der Jeugd et al., 2002). Geese tent to quite frequently adopt young goslings from neighbouring broods which may result in parental resources being provided to non-kin and can have major effects on the cost and benefits of parental care and individual strategies (Choudhury et al., 1993). Settling close to kin lowers the risk of adopting non-kin goslings.
Geese are highly philopatric, meaning that they return to the same nesting locations year after year (Loonen et al., 1997) giving them knowledge about local conditions (Rockwell et al.,
1993) and as their offspring is philopatric as well they increase relatedness and thereby kin selection and inclusive fitness.
J. van Eerbeek, 2013 Effectivity of Dutch Goose management during the breeding season 5 Geese form lifetime pair bonds and the females' success is attributable to the males' qualities enabling the acquisition of good territories (Black, 2001; Black & Owen, 1995). Loss of this pair bond by decease of a partner means a loss of knowledge and teamwork (Black, 2001).
Females generally grow older than males, because males participate in fights, protect the nest against other males and fend off predators. The female then has to resort in choosing another male from a much younger cohort which are mostly inexperienced resulting in loss of the nest site and higher chick mortality (Black, 2001; Rockwell & Cooch, 1993).
In colonial animals the individuals with the best physical condition and best advantages through kin selection probable have the best territories which give them the highest direct and inclusive fitness producing most offspring (Watson et al., 1994; Van der Jeugd et al., 2002).