Projects

Applied research at Altenburg & Wymenga consultancy firm

Advice and research on meadow bird management
Meadow bird management is an important part of nature-inclusive agriculture. The Netherlands plays a major role internationally as a breeding area for meadow birds such as Black-tailed Godwit, Lapwing, Oystercatcher and Shoveler. The meadow birds are not doing well, despite the many efforts being made to turn the tide. A&W has been involved in many of these efforts for years and has a lot of experience in management and deep-rooted knowledge of the ecology of meadow birds, and not only on farmland but also in reserves. We support agricultural collectives, site managers and also governments with ecological knowledge. Moreover, as predation is an important factor in the breeding success of meadow birds, A&W is closely involved in research into the role of predation. The Provinces use the results for their policy in the field of meadow bird and fauna management.

Geese research and management
In recent decades, geese populations have increased significantly in NW Europe due to changes in hunting pressure and shift of wintering areas from wet nature reserves or extensively managed farmland to intensively managed agricultural areas. Geese foraging in agricultural areas cause considerable economic damage to agricultural crops in the Netherlands and in recent years the amount paid out has increased sharply. In the Dutch policy on wildlife damage, in order to qualify for compensation, landowners are personally responsible for limiting wildlife damage using non-lethal preventive measures. Today, a wide range of devices to deter geese are in use, although their effectiveness is variable due to habituation. At Altenburg & Wymenga we carried out studies in The Netherlands to build up on knowledge to limit agricultural damage caused by geese. We investigated the effects of timing and intensity of grazing pressure and environmental variables on grass growth during spring in 3 years. We found that a longer period of grazing pressure and a higher grazing intensity led to shorter grass at the time of mowing. In addition, as grass growth is also determined by spring temperature and rainfall, in a cold or dry spring the grass gets off to a worse start and recovers poorly after grazing. Moreover, we investigated the effectiveness of the bio-acoustic device BirdAlert® as measure to keep geese out of damage-sensitive fields. We found that on plots with “BirdAlert plus” treatment (device plus gas cannon and “Scareman”), there were significantly fewer geese droppings counted compared to control plots.

Disturbance on protected areas and species

With new spatial developments and existing use, the question is often asked whether protected areas and species will be disturbed. Disturbance can occur during the construction of a road, industrial estate, residential area, through recreational activities, or through shooting by hunters. To know whether disturbance really matters ecologically in a particular situation, knowledge and sometimes targeted field research are needed. For example, into the behavior and flight responses of animals and into disturbance distances.
To determine the effects of disturbance on breeding meadow birds, wintering geese and wildfowl, rules of thumb are often used with distances for different sources of disturbance. A&W has formulated requirements that must be met and these distances have subsequently been tested, substantiated and fine-tuned. We regularly apply this knowledge to determine whether interventions can lead to disturbance in bird populations. Field research into disturbance has be often done remotely with a rangefinder (binoculars with laser) so as not to cause disturbance ourselves.

Wind energy and birds
Paint it black?
A study on the island of Smøla, Norway, tested whether painting one blade of a wind turbine black reduces the number of bird collisions (May et al. 2020). Although the results were positive for e.g. white-tailed eagle, there is need for a more elaborate study in a more species-rich environment. In September 2021 we started a three-year study in windfarm Eemshaven in the Netherlands. This windfarm is located in an area with high intensity of bird flight movements, resulting in high mortality rates among a wide variety of species. The research is set up following a BACI design (Before–After–Control–Impact) where monitoring of collision fatalities is carried out at a selection of 14 wind turbines. The rotor blades of seven of these turbines were painted black in August – September 2022. Here we present the results of the null monitoring that was carried out between September 2021 and September 2022. The species composition of the fatalities was dominated by gulls and small songbirds, but also several geese, ducks and shorebirds were found. Although we excluded any dead birds from the analysis that were likely to have other causes of death, bird flu may have had an impact, for example when sick and disoriented birds eventually collided with one of the turbines. In total 54 species were found. The number of fatalities was almost equally divided over the impact turbines (still with white rotor blades) and control turbines. A t-test showed no significant difference in the number of fatalities between both sets of turbines. However, at the level of the individual turbines, there are major differences in both the spatial and seasonal distribution of fatalities. These seasonal patterns reflect the migration patterns of waterfowl, shorebirds and songbirds, whereas the spatial patterns probably reflect the location of the turbine and its distance to the coast. The results of the null monitoring give a solid basis for testing the impact of painting one rotor blade black. The impact monitoring is currently running, and at the end of 2024 the final results of the study will be known.

PhD project

In my PhD project I investigated the maintenance of colour polymorphism in a Dutch population of a very variable bird of prey, the Common buzzard Buteo buteo.
Persistent plumage colour polymorphism occurs in around 3.5% of bird species, with raptors showing a disproportionately high frequency of such polymorphisms. These polymorphisms are interesting from an evolutionary perspective, because they are heritable and hence a good model for understanding mechanisms preserving genetic variation. Balancing selection is a major mechanism to maintain colour polymorphisms over evolutionary time. In Common buzzards, variation in plumage colour was reportedly maintained by a heterozygote advantage: heterozygote intermediates had higher fitness than homozygote light and dark morphs.

Chapter 1
For evolutionary models, it is important to assess whether discrete morphs exist or whether variation is more continuous. Using image analysis, I showed that in Common buzzards variation is continuous and unimodal, ranging from very dark to very light individuals. Previous studies on Common buzzards have used a classification with three discrete morphs. I compared this classification with a seven-scale morph classification used in my study. I used photographs of the same individuals taken at different ages. Even though the plumage gets somewhat darker from juvenile to adult age, morph type did not change substantially.

Chapter 2
I challenged one of the basic premises of the heterozygote advantage hypothesis, by testing whether plumage colour variation in Common buzzards follows a one-locus two-allele inheritance model. Using a long-term population study with 202 families, I showed that colour variation in buzzards is highly heritable. However, I found no support for a simple Mendelian one-locus two-allele model of inheritance. My results rather suggest that buzzard plumage colour should be considered a quantitative polygenic trait.

Chapter 3
I took advantage of 20 years of life history data collected in a Dutch population to replicate earlier studies on fitness consequences of colour polymorphism in the Common buzzard. I examined morph differences in adult apparent survival, breeding success, annual number of fledglings produced and cumulative reproductive success. I found that fitness (cumulative reproductive success) differed among morphs, with the intermediate morph having highest fitness. Assortative mating for colour morph was observed, and I found that assortative pairs were more likely to produce offspring than disassortative pairs, and their pair bonds lasted longer. Over our long-term study I found a phenotypic change with an increasing proportion of intermediate morphs.

Chapter 4
I described natal dispersal behaviour in the emigration and wandering stages of 64 individuals tagged with GPS transmitters. I found that morphs only differed in the number of areas visited, but melanic coloration did not affect other traits such as emigration timing, distance travelled and proportion of forested habitat chosen. I found that darker buzzards visited a higher number of residency areas during the first months of their wandering stage compared to lighter individuals.

“Buteo-morph” citizen science project
In this project I aimed to investigate the geographical and temporary differences in
the distribution of the various morph-types in the Common buzzard across Europe. The
individual performance of different morphs may depend on habitat characteristics and
could vary in space at a small or large scale. Potential spatial variation in morph frequencies are largely unexplored. I involved birdwatchers and citizen scientists from many countries to collect information on the distribution of different morphs all year round between 2015 and 2018.

Scientific collaboration

The Collared flycatcher Ficedula albicollis has been little studied in Italy despite being included in the Annex I of Directive 147/09/EC. In this study I collected more than two hundred presence points of the species in the Appenines of Abruzzo region. My colleagues and I considered eight climatic and environmental variables as potential predictors of the habitat distribution of Collared flycatchers in central Italy for the months of April-July, equivalent to the period of presence of the species in the reproductive area. Forest typology and two climatic variables (maximum temperature and average rainfall) were the parameters that contributed most to the habitat distribution model, while the variables related to the morphology of the territory did not seem to be relevant.

MSc project

Climate change may cause phenological asynchrony between trophic levels, which can lead to mismatched reproduction in animals.
In my master project I described direct effects of trophic mismatch and nestling age on prey choice in pied flycatchers (Ficedula hypoleuca), a migratory bird.
I used camera trap data collected over the breeding season of 2012 and found that the mismatch with the caterpillar peak negatively affected numbers of caterpillars and offspring condition, and positively affected numbers of flying insects in the nestling diet. Feeding more flying insects was negatively correlated with nestling day 12 mass. Data showed preferential feeding of spiders when nestlings were <7 days old. Receiving more spiders during this phase was positively correlated with tarsus growth.