Birds would die

The great bird death

Interview with the bird protection expert Lars Lachmann

Our bird world is doing badly. At least that's what you get when you follow the reports in the media. What is it and what are the possible causes? An interview with bird protection expert Lars Lachmann.

Cranes are on the up - but what about other bird species? - Photo: Thomas Munk

There is hardly a report about an interesting bird species that does not indicate that it is endangered. However, we have been hearing these reports for years, and yet we still see birds outside in the garden, some - like crows and magpies - even seem to be on the rise. And weren't there the occasional cheers from the nature conservation associations about the increase in the populations of sea eagles, cranes or peregrine falcons?


Mr. Lachmann, how is the bird world actually doing?

Fortunately, our birds belong to the best-studied groups of living beings, and the data on their populations and population developments - compared to other animal groups such as insects - are excellent. Birds are therefore particularly suitable as indicators of the state of our nature. Every six years, the federal government has to report to the EU Commission exactly on the situation of all bird species in Germany so that it can assess how well the EU's bird protection directive is being implemented in Germany. A corresponding report was last drawn up in 2013. A look at this data should quickly answer the question of whether or not there is bird death. But it is not that simple. At first glance, one could even lean back and relax: for the longest period under consideration, the 25-year trend, slightly more species of 242 breeding bird species are increasing than decreasing.


The star, whose population has almost halved in recent years, is particularly affected. - Photo: Norbert Parmantye / www.naturgucker.de

If you take a differentiated look at the individual species, it becomes clear that these increases mainly affect very rare bird species, but that it looks bad for the bird species that one would actually expect in large numbers across the country. That explains the occasional cheers: The populations of particularly rare species such as crane, sea eagle or peregrine falcon are back again, as we can protect them through legal regulations and the establishment of nature reserves. Bird death, however, takes place with the bird species that should actually occur everywhere in the so-called normal landscape.

That means that the protective measures for rare bird species are taking effect. First of all, that's positive. But what about the other types? Are blackbirds, finches and starlings dying out?

These species will not become extinct, but their populations are at risk. It could be that in the future you have to go to the next nature reserve to see these common birds. NABU recently calculated the existing population figures and trends at the individual level. The trend here is extremely worrying: While the number of birds apparently remained almost stable between 1990 and 1998, 15 percent of all breeding pairs in Germany disappeared between 1998 and 2009 - even though a look at the species level shows winners and losers keep the scales. So in just twelve years we have lost around 12.7 million breeding pairs of birds.


Bird mortality figures - Graphic: NABU

The next complete report by the federal government on the state of the bird world is due in 2019. Can you already say how things have progressed over the past few years?

The Dachverband Deutscher Avifaunisten (DDA) has evaluated the available data in great detail - again at the species level - in order to find out what distinguishes bird species whose populations are declining particularly often. In summary, one can say that a bird species has particularly poor prospects if it is a widespread, frequent songbird that breeds in the agricultural landscape and feeds primarily on insects and therefore spends the winter as a migratory bird in Africa. For these species, the declines have certainly continued in a similar manner in recent years. For other species, the drastic decline will turn out to be part of natural population fluctuations. So it will be interesting to see what news the next bird protection report will bring. I wouldn't be particularly optimistic.

What are the reasons for this massive loss of animals?


Most songbirds feed their young with protein-rich insect food. - Photo: Rita Priemer

There are many different causes of death for birds, such as predators, hunting or windmills. Studies show, however, that the dramatic loss in recent years can be explained less by the increased death rate among adult birds than by the fact that not enough young birds are raised. This happens when birds cannot find a suitable habitat or enough food.

Most songbirds feed their young with protein-rich insect food, even if the adult birds, like our sparrow species, prefer vegetarian food themselves. Migratory birds mainly feed on insects. The recently published results of a long-term study, which showed a decrease in the number of flying insects of 76 percent within only 27 years for 63 nature reserves, mostly located in north-west Germany, are therefore extremely worrying. Neither climatic factors nor other changes in the examined areas could explain such a drastic decrease, which is why the researchers suspect that it could be due to influences from the surrounding agricultural fields for which they did not have any evaluable data.


Impairments and threats to all breeding bird species in Germany. - Source: Bird Protection Report of the Federal Government 2013

When the insects die, the insectivores die too, that makes sense. But you said that the birds in the agar landscape are also threatened. Accordingly, not only the death of insects but also the death of birds seems to have something to do with changes in agriculture. What has changed in our fields and meadows in recent years that can explain such dramatic consequences?

A development is advancing across Germany that can be summarized under the term “agricultural intensification”. In addition to the use of new types of pesticides, this includes the increasing mean size of farms and the associated enlargement of individual fields, a decline in meadows and pastures compared to arable land, increased mowing frequencies on remaining grassland, increasing stables for cattle, drainage of wet meadows, increased fertilization and a reduced diversity in the cultivated arable crops with an increasing dominance of only three plant species, namely winter wheat, maize and rapeseed. At the same time, so-called marginal yield sites that have been used extensively so far are being completely removed from management and are therefore no longer used as open-land habitats.

A change that is particularly decisive for field birds is the rapid decline in temporarily unmanaged fallow land, which was around 90 percent between 1994 and 2011 and has continued since then. In return, the cultivation area of ​​maize, which does not offer suitable breeding or feeding opportunities for bird species, increased. This extremely rapid development of the loss of fallow land with simultaneous expansion of maize cultivation coincides exactly with the observed accelerated decline in widespread and frequent songbirds, especially in open land. Changes in the way we manage our agricultural landscape are therefore the key to the urgently needed turnaround. We need a new agricultural policy that is compatible with nature.

Thank you for talking to us!


Further deadly dangers for the domestic bird world


The influence of domestic cats (20 to 100 million victims per year)

Domestic cats eat birds, that's for sure. However, there is currently no reliable estimate of the number of birds that fall victim to domestic cats in Germany. With around 12.9 million domestic cats fed and perhaps one to two million completely independent feral domestic cats, NABU believes that 20 to 100 million dead birds per year are realistic, with the upper end of this spectrum appearing more likely.

That sounds like a lot at first. This number has to be seen in relation to the total number of birds dying each year. Then domestic cats cause only 4 to 20 percent of all bird deaths. That is still a lot, but among other things, the results of the NABU counting campaign “Hour of the Garden Birds” since 2005 show that the general species populations in the settlement area, i.e. where domestic cats hunt, are stable. In addition, there are no differences in the bird frequency between gardens with or without cats at the “hour of the garden birds”. So other species tend to decrease in habitats that are less visited by cats. The decisive argument against cats as the main cause of bird death, however, is that the cause must be a factor that has recently been added or has a significantly increased effect. However, the number of cats has only increased very slightly for years and can therefore be ruled out as the cause of the marked decline in the population after 1998. Of course, this does not mean in reverse that cats do not have any negative effects on bird populations. It is quite conceivable that bird populations in our settlement areas could be significantly higher without the influence of cats.

More about the dangers posed by domestic cats

The influence of corvids

In contrast to cats, corvids, i.e. magpies, jays or carrion and hooded crows, are natural predators for which young birds in particular are regularly on the menu. The populations of these common raven bird species also did not increase or only increased slightly during the period under review, even if a shift of the populations away from open land to the settlement areas in some gardens suggests an increase. Any bird lover who has observed a magpie plundering a bird's nest is quickly tempted to suspect the cause of the bird death in such raids. What is overlooked is that such predations of nests have always taken place and are no more common today than they used to be. In the “hour of the garden birds” there was no effect of the frequency of magpies in a garden on the frequency of other birds. The corvids are also ruled out because of the cause of the current bird deaths.

More about the dangers posed by corvids

The impact of collisions on glass panes (100 to 115 million victims per year)

In numerical terms, one of the most important causes of bird death is undoubtedly the collision with glass panes. The national working group of the state bird protection centers published an estimate of 100 to 115 million glass approach victims in Germany in 2017. Birds in settlement areas are particularly affected, but also migratory birds on their migrations. Usually these are small, common bird species, but rarer species such as woodcock, kingfisher or hawk also appear disproportionately affected. In addition, the number of glass structures in Germany is definitely increasing, while the use of preventive measures, such as certain printed patterns on the glass panes, has not yet become standard. Bird death on panes of glass can therefore have a share in the decline in songbirds. However, it can again be ruled out as the main cause, since the slow rise in glass structures does not correlate with the sudden decline in the number of birds, and because the birds in the settlement area would again have to be disproportionately affected.

More about the hazard from glass panes

The impact of collisions in road and rail traffic (70 million victims per year)

Fatalities from collisions between birds in road and rail traffic are estimated at around 70 million for Germany. The risk rises continuously as the volume of traffic increases. Birds in the settlement area as well as in the open country or in the forest are affected. However, larger bird species such as birds of prey or owls hunting at night are disproportionately endangered by vehicle collisions. In these species, this factor could therefore lead to population declines or endanger ongoing populations. The current bird deaths, however, mainly affect smaller species, and the continuous slow increase in traffic does not match the marked drop in the number of birds.

The influence of power lines (1.5 to 2.8 million victims per year)

Birds also regularly collide with power lines. A 2017 NABU study estimated that 1.5 to 2.8 million birds per year die when they approach a power line. With the expansion of the transmission network in the course of the energy transition, this number could increase further if no suitable countermeasures are taken. Larger bird species that are less agile in flight, especially water birds, are selectively affected by this cause of death. However, this factor can also be ruled out as a major cause of the decline in smaller, widespread bird species.

More about the hazard from power lines

Power lines can also electrocute birds if a bird grounds a line through contact with the mast. This problem occurs selectively only in large birds such as storks, owls or birds of prey and has been shown to be a population-threatening factor for these species. It is estimated that around one million large birds die each year in Germany. Fortunately, this number is falling significantly in this country, as, thanks to a legal requirement, all electricity pylons had to be secured against bird strikes by the end of 2012. The problem has not yet been completely resolved, however, as the implementation has not yet been completed and, for example, the overhead lines of the railway have so far been excluded. However, the currently observed bird deaths are independent of this factor, since electrical death affects a different spectrum of species and its significance is greatly reduced.

More about the "electric death"

The impact of wind turbines (100,000 casualties per year)

The risk of birds colliding with wind turbines increases significantly as the number of wind turbines increases. One has to assume that over 100,000 birds are killed by wind turbines each year, including around 12,000 common buzzards and 1,500 red kites. In absolute numbers, that is a small number compared to the millions of birds that fall victim to cats, panes of glass or traffic. Larger bird species are particularly affected, however, especially birds of prey. For some of these species, wind turbines can already have an impact on the population today, but wind turbines are not relevant for the mass of the mostly smaller and frequent but declining bird species.

More about the dangers posed by wind turbines

The influence of the hunt (1.2 million victims per year)

Legal hunting in Germany currently kills around 1.2 million birds out of 30 huntable bird species, and 53 million birds out of 82 species across the EU. In addition, there are an estimated 50,000 to 150,000 illegally killed birds across Germany, and 12 to 38 million victims of illegal persecution are estimated for all of Europe and the Mediterranean region. Overall, at least the number of legally hunted birds is clearly decreasing, as the number of active hunters is also decreasing.

In Germany, the hunt is mainly limited to ducks and geese, which are currently mostly showing good population developments. One exception is the still ongoing hunt for partridges, which, with a population decline of 94 percent in just twelve years, are among the biggest problem children of the current bird deaths. It has recently been proven across Europe that the annual kill of 1.5 million lovebirds is more than this species, which is already rapidly declining, can cope with. Poaching in Germany primarily threatens protected birds of prey such as sea eagles, red kites and hawks, of which an estimated 1,200 to 12,000 are killed each year. Hunting and poaching are therefore possible population-influencing factors for some particularly affected species such as partridge, lapwing and birds of prey. However, they do not affect most of the currently declining bird species.

More on legal bird hunting

More about illegal bird hunting

The influence of new diseases like Usutu and Trichomoniasis

When looking for possible causes for the disappearance of birds, reference is also made to novel diseases. In fact, there have been two novel diseases in recent years that are clearly noticeable in two species of birds. Since 2011 we have been observing blackbird deaths in Germany that are triggered by the Usutu virus, which is new in Germany. So far, however, it only occurs in climatically favored regions, especially along the Rhine Valley. Since then, an estimated 160,000 blackbirds have died of this disease every year.In the areas affected by the Usutu virus, the population trend of the blackbird is significantly more negative than in areas without Usutu, but no effects could be detected in other bird species. It is unclear whether the regionally depleted blackbird populations will normalize again in the future. So far, however, no effect of these regional decreases on the national population trend of the blackbird or any other bird species has been demonstrated. Due to the expected spread of the virus to other areas of the country, long-term threats to the existence of the virus are conceivable, at least for the blackbird.

More about the Usutu virus

The so-called greenfinch death, however, is caused by a single-celled parasite called Trichomonas gallinae triggered, of which a particularly aggressive variant has been circulating in Germany since around 2009. Greenfinches usually become infected at feeding or bathing areas and watering areas in summer. Other bird species such as lovebirds or hawks also suffer from this so-called trichomoniasis, but infections in green finches in particular seem to be more fatal. Since 2013, the numbers of green finches at the "hour of garden birds" have suddenly decreased by 43 percent, and the monitoring of the umbrella association of German avifaunists (DDA ()) has since shown a significant decrease in the population, which is probably due to this disease Disease is a possible cause of sudden populations in certain species, but in this case the epidemic does not begin until after the reference period for the observed bird deaths.

More about the death of greenfinches


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Lars Lachmann treats the topic in more detail in the article "The great bird death: fact or fake?", Which appeared in the Loccumer protocols. You can download the publication here. The entire booklet can also be ordered from the Evangelical Academy in Loccum.


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