Thomas Bregnballe

Aarhus University | AU · Department of Bioscience

Measuring success or failure in the conservation of seabirds depends on reliable long-term monitoring. Traditionally, this monitoring has been based on line transects and total or point counts, all of which are sensitive to subjective interpretation. Such methods have proven to consistently record fewer individuals than intensive efforts, while req...

Human development around the globe has led to great expansion of the Brown Rat (Rattus norvegicus), which has implications for local wildlife and especially ground-breeding birds. In this study, we analyse the colonisation and persistence of rats on small islets important to breeding waterbirds in a Danish fjord, and investigate the effect of rat p...

We describe long-term changes in the distribution of 2249 freshly dead winter recoveries of 94,352 Great Cormorant chicks ringed between 1940 and 2018 in Denmark. The entire wintering range was divided into four major compartments to assess changes in (1) migratory distance and (2) the spatial distribution of recoveries. In the south-eastern winter...

The recovery of the Baltic White-tailed Eagle Haliaeetus albicilla population since the 1980s is a conservation success story. However, the re-establishment of this predator in coastal and lake areas appears to affect Great Cormorants Phalacrocorax carbo during the breeding season. We collated published and unpublished records of White-tailed Eagle...

Great Cormorants were censused on a pan-European level in January 2013. Cormorants were found in an enormous winter range, spanning from the Baltic Sea and Atlantic Ocean in the north to the Mediterranean and coasts of North Africa. This large-scale exercise in which more than 5000 volunteers took part resulted in a total of 641,650 Cormorants coun...

Density-dependent depletion of prey during the breeding season may affect breeding performance and colony development in seabirds and colonial waterbirds. Breeding Great Cormorants Phalacrocorax carbo sinensis are central place foragers, so parental flight distances to profitable foraging grounds and thus parental provisioning of offspring are like...

After a period of continuous increase and range expansion, the Baltic Great Cormorant population has stabilised in large parts of its range in recent years. Ringing recoveries reveal that considerable proportions of the population winter in areas that can be affected by prolonged frost periods. There is evidence that winter severity is an important...

The use of Unmanned Aerial Vehicles (UAVs) to monitor large colonies of seabirds avoids challenges associated with conventional methods, but manual image processing is expensive. Development of semi-automated analytical methods rely on high image spatial resolution, which requires a trade-off between securing low area coverage and high spatial reso...

Monitoring breeding seabirds is fundamental for conservation, but conventional methods face several challenges. The use of UAVs is a powerful tool to monitor large colonies of seabirds in remote areas causing low disturbance, but these surveys require that large amount of data needs to be accurately transformed. In general, this process is highly t...

I nærværende projekt har DCE - Nationalt Center for Miljø og Energi, Aarhus Universitet undersøgt, hvorvidt droner egner sig til optælling af fugle, der yngler i kolonier såsom skestork, måger og terner. Forsøgene har vist, at droner kan være mindre forstyrrende, fordi man ved brug af en drone kan undgå at bevæge sig rundt i kolonierne og dermed sk...

Populations of migratory birds often mix to a considerable extent in their wintering areas. Knowledge about the composition of wintering populations is highly relevant to management, not least for species such as the great cormorant Phalacrocorax carbo sinensis, prone to conflicts with human interests. However, few studies have been able to estimat...

The Cormack-Jolly-Seber (CJS) model assumes that all marked animals have equal recapture probabilities at each sampling occasion, but heterogeneity in capture often occurs and should be taken into account to avoid biases in parameter estimates. Although diagnostic tests are generally used to detect trap-dependence or transience and assess the overa...

Observations made of disturbance to spring staging Wigeon Anas penelope and Teal A. crecca by human and "natural" (non-human) stimuli at a restored wetland in the Skjern River delta, Denmark, were analysed to inform future management of human access to the site. The effects of human activity (anglers, cyclists, farming activity) on the flight respo...

Disturbance of birds by human recreational activities – an overview Studies during the last thirty years show that the increasing recreational use of the countryside often has adverse effects on wildlife, including birds, which perceive humans as potential predators. Ultimately, the effect is that the birds are prevented from using some of the othe...

I denne rapport præsenteres resultaterne af den optælling af skarvreder, som fandt sted i de danske skarvkolonier i foråret 2017. I 2017 var der 33.171 par ynglende skarver i Danmark. Det var 1.493 flere par end i 2016, hvilket svarer til en fremgang på 4,7 %. Årene 1993-2006 var karakteriseret ved en stabil ynglebestand på omkring 39.000 par, hvor...

This report presents the results of the annual count of all apparently occupied Great Cormorant nests throughout Denmark. In 2017, a total of 33,171 nests were registered, which is 1,489 nests more than in 2016, corresponding to an increase of 4.7%. In Denmark as a whole, the Cormorant breeding population maintained stable numbers at around 39,000...

I denne rapport præsenteres resultaterne af den optælling af skarvreder, som fandt sted i de danske skarvkolonier i foråret 2016. I 2016 var der 31.682 par ynglende skarver i Danmark. Det var 324 flere par end i 2015, hvilket svarer til en fremgang på 1,0 %. I 2016 var antallet af ynglende skarver således stort set uændret i forhold til 2015. Årene...

This report presents the results of the annual count of all apparently occupied Great Cormorant nests throughout Denmark. In 2016, a total of 31,682 nests was registered, only 324 nests more than in 2015, corresponding to an increase of 1.0 %. In Denmark as a whole, the Cormorant breeding population maintained stable numbers at around 39,000 pairs...

I denne rapport præsenteres resultaterne af den optælling af skarvreder, som fandt sted i de danske skarvkolonier i foråret 2015. I 2015 blev der registreret 31.076 ynglepar af skarver i Danmark. Årene 1993-2006 var karakteriseret ved en stabil ynglebestand på omkring 39.000 par, hvorefter antallet gik tilbage. I 2010-2013 lå ynglebestanden på et n...

This report presents the results of the annual count of apparently occupied Great Cormorant nests in Denmark. In 2015 a total of 31,076 nests were recorded in Denmark. The years 1993-2006 were characterised by a stable breeding population around 39,000 nests, whereafter numbers fell to around 26,400 nests in 2010-2013 (Fig. 1). Breeding numbers inc...

We review the current and future threats to duck populations that breed, stage, moult and/or winter in the Nordic countries. Migratory duck species are sensitive indicators of their changing environment, and their societal value confirms the need to translate signals from changes in their distribution, status and abundance into a better understandi...

A review report, providing national and international knowledge/documentation about the impact of predation in freshwater. Mammals and birds are included, but the main focus is on cormorant predation.

A total of 45 countries were contacted to participate in the pan-European roost count census action, organized within the EU Commission funded initiative ‘CorMan’ in cooperation with the IUCN/Wetlands International Cormorant Research Group. Due to the huge effort and support given by all the National Coordinators who were in charge and responsible...

IUCN Cormorant Research Group Bulletin, 8, pp. 7-8

Changes in the breeding population of Black-headed Gulls Chroicocephalus ridibundus in Denmark 1970-2010 This paper describes the changes in the breeding population of Black-headed Gulls in Denmark based on estimates of national and regional breeding numbers in 10 survey years between 1970 and 2010. We extracted more than 10000 published and unpub...

Changes in the breeding population of Black-headed Gulls Chroicocephalus ridibundus in Denmark 1970-2010 This paper describes the changes in the breeding population of Black-headed Gulls in Denmark based on estimates of national and regional breeding numbers in 10 survey years between 1970 and 2010. We extracted more than 10000 published and unpubl...

Although numbers of breeding Pied Avocets in Denmark increased between the 1920s and the early 1990s, they are now declining significantly more rapidly than in almost all other NW European countries. There have been few studies of the causes of the declines in breeding colonies in Denmark, and here we analyse some case studies and overall trends in...

Development of the breeding population of Pied Avocet Recurvirostra avosetta in Denmark 1970-2014 This paper describes the development of the breeding population of Pied Avocets in Denmark based on national censuses conducted in 1970, 1980, 1990, 1996, 2009 and 2014. Our estimates of total breeding numbers of Avocets in Denmark deviate from some of...

Development of the breeding population of Pied Avocet Recurvirostra avosetta in Denmark 1970-2014 This paper describes the development of the breeding population of Pied Avocets in Denmark based on national censuses conducted in 1970, 1980, 1990, 1996, 2009 and 2014. Our estimates of total breeding numbers of Avocets in Denmark deviate from some of...

Although numbers of breeding Pied Avocets in Denmark increased between the 1920s and the early 1990s, they are now declining significantly more rapidly than in almost all other NW European countries. There have been few studies of the causes of the declines in breeding colonies in Denmark, and here we analyse some case studies and overall trends in...

After circa 35 years of drainage and intensive arable tillage, the lower Skjern River, Den-mark was re-engineered to its original meanders and flooding regime, creating 22 km 2 of lakes, shallow wetlands and seasonally flooded grazed wet grassland costing €38 million. The primary motivation was to restore the sediment/nutrient retention capacity of...

Denne rapport samler og sammenstiller eksisterende viden om betydningen af prædation fra fugle og pattedyr på bestande af ferskvandsfisk. Der anvendes både offentliggjorte og ikke-offentliggjorte resultater fra danske og udenlandske undersøgelser. Både mink, odder, skarv og fiskehejre æder betydelige mængder fisk og kan derfor formodes at have en v...

I denne rapport præsenteres resultaterne af den optælling af skarvreder, som fandt sted i de danske skarvkolonier i foråret 2014. I 2014 var der 30.503 par ynglende skarver i Danmark. Det var 5.801 flere end i 2013, hvilket svarer til en fremgang på 23 %. Yngleantallet i 2014 blev dermed højere end i de foregående fire år, hvor yngleantallet varier...

This report presents the results of counts of Great Cormorant Phalacrocorax carbo sinensis nests in breeding colonies in Denmark in the spring of 2014. Great Cormorants were breeding at 76 different localities with a total of 30,503 breeding pairs (nests) in Denmark in 2014. This is an increase of five colonies and 5,801 nests (23%) since 2013. Bre...

This report presents the status of the breeding population of Great Cormorants Phalacrocorax carbo in Europe and neighbouring countries in 2012. It gives an overview of numbers and distribution and describes changes since 2006. It compiles 38 detailed national and sub-national reports on breeding numbers, colony sizes, colony distribution and the e...

We use results from monitoring the breeding population of Great Cormorants Phalacrocorax carbo in the Western Palearctic in 2006 and 2012 in order to present an overview of numbers and distribution in 2012 and to describe the major changes since 2006. In 2012 the continental sub-species P. c. sinensis was breeding in almost all countries in Europe...

After circa 35 years of drainage and intensive arable tillage, the lower Skjern River, Den-mark was re-engineered to its original meanders and flooding regime, creating 22 km 2 of lakes, shallow wetlands and seasonally flooded grazed wet grassland costing €38 million. The primary motivation was to restore the sediment/nutrient retention capacity of...

Med genopretningen af Skjern Å-systemet fra Borris i øst til udløbet i Ringkøbing Fjord mod vest blev der skabt et stort sammenhængende område bestående af lavvandede søer, rørskove, sumpe samt våde og tørre enge. Allerede før etableringen af vådområderne blev afsluttet i foråret 2002, blev områderne taget i brug af et stort antal vandfugle. På gru...

Med hensyn til ynglefuglene konkluderer vi, at naturgenopretningen har bragt Skjern Enge op blandt Danmarks 10 bedste yngleområder for vandfugle. Vådområdet har især givet gode ynglebetingelser for lappedykkere og andefugle. Derudover har enkelte Bilag I arter og rødlistede arter ynglet. De mere sjældne engfugle og engfugle i større antal har ikke...

This report is a compilation of national reports from 23 of the countries that conducted national surveys of the sizes and distribution of breeding colonies of Great Cormorants Phalacrocorax carbo in parts of the Western Palearctic in 2012 (though one country covered only in 2011). The national surveys were conducted in coordination with the Pan-Eu...

Population development of Common Tern Sterna hirundo in Denmark, 1970-2012 The Common Tern is an Annex I species on the EU Birds Directive. It is designated as a breeding species for 30 of the Danish SPAs. Knowledge about breeding occurrence of terns has been collected mainly in projects and surveys initiated and carried out by volunteers, in some...

Population development of Common Tern Sterna hirundo in Denmark, 1970-2012 The Common Tern is an Annex I species on the EU Birds Directive. It is designated as a breeding species for 30 of the Danish SPAs. Knowledge about breeding occurrence of terns has been collected mainly in projects and surveys initiated and carried out by volunteers, in some...

Med igangsættelse af det Nationale program for Overvågning af VAndmiljø og NAtur (NOVANA) har Danmark fra 2004 fået en systematisk overvågning af bl.a. fugle omfattet af Fuglebeskyttelsesdirektivet. I henhold til dette direktiv og Habitatdirektivet er der udpeget et netværk af særlige beskyttelsesområder, kaldet ”Natura 2000-områder”, som rummer ar...

Cormorants are often casually referred to as ‘big black birds’. However, within well-defined ranges of course, they come in a variety of structural sizes and plumage colourations (see Figure 5.1 and others in this chapter). These differences in plumage colouration and structural size, if carefully and systematically recorded, can give valuable insi...

This chapter focuses on Cormorant population counts for both summer (i.e. breeding) and winter (i.e. migration, winter roosts) seasons. It also explains differences in the data collected from undertaking ‘day’ versus ‘roost’ counts, gives some definitions of the term ‘numbers’, and presents two examples of how numerical data can be used to calculat...

Cormorants move extensively around continental Europe and beyond. After the breeding season young Cormorants first start to explore the environment around the nesting site thereafter they, as well as most adults, disperse in different directions, before initiating the real autumn migration. Not all Cormorants migrate south, indeed some remain withi...

Parasites are considered to be a key driver of evolutionary processes in wild animal populations. However, assessing host‐endoparasite burdens non‐destructively is problematic. Collection of faecal samples can be difficult, and faecal egg counts may not always be a reliable indicator of infection intensity. Here we report on endoscopy as a method f...

In most bird species timing of breeding affects reproductive success whereby early breeding is favoured. In migratory species migration time, especially arrival at the breeding grounds, and breeding time are expected to be correlated. Consequently, migration time should also have fitness consequences. However, in contrast to breeding time, evidence...

The work of this paper is motivated by a study of Great Cormorants, Phalacrocorax carbo sinensis, in Denmark. The dataset is complex, involving birds in different states living in and moving between neighbouring colonies. As a consequence, the set of probability models that might describe the data is large. In order to choose between the models, we...

NATURA 2000-planernes indsatsprogram indeholder retningslinjer, hvorefter statslige myndigheder er forpligtet til at følge direkte op på NATURA 2000-planen i form af bekendtgørelser og lignende uden forudgående handleplanlægning. Naturstyrelsen skal som ansvarlig myndighed følge op på NATURA 2000-planerne i form af reservatbekendtgørelser, hvis det...

We examine the performance of a method of integrated population modelling for the joint analysis of different types of demographic data on individuals that exist in, and move between, different sites. The value of the approach is demonstrated by a simulation study which shows substantial improvement in parameter estimation when site-specific census...