Beavers facilitate Teals at different scales

Wetland ecology group_University of Helsinki_Teal

Teal broods utilize beaver ponds.

Blog text by Petri Nummi, Eeva-Maria Suontakanen, Sari Holopainen and Veli-Matti Väänänen “Beavers facilitate Teals at different scales” is now available on the Ibis website.

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There and back again – a mire’s tale

In a remote country lived a rich mire species community. But that was once upon a time, when Finland was a land of mires. Nowadays, only fragmented pieces are left in the southern region, while large natural mires can still be found in Lapland. Nevertheless, only one third of historical levels remain. Most mireswere dried due to farming and forestry. Ditches were dug to gather water from ca. 6 million hectares of mires. This affected the hydrology and further the ecology of these wet ecosystems. Several plant and animal species are adapted to mires, and have thus suffered from habitat loss and fragmentation. For example, forest grouse and bean geese (Anser fabalis) utilize mires during their breeding period. Due to ditching, mires stop producing their ecosystem services, because berry production and game bird populations (these are cultural and provisioning ecosystem services), decrease, and thus the recreational values of the areas lessen.

Wetland ecology group_University of Helsinki_Mire_Cloudberry

Cloudberry (Rubus chamaemorus) grows on mires and benefits from restoration activities.

Finland has about 10 million hectares of dried mires, more than half of which have been utilized by forestry. However, about a fifth of this area does not produce wood well enough for it to be profitable. After several centuries of mire destruction,  a change is now in the air. Finnish mires are being restored with increasing effort. For example, in 2017 Metsähallitus (the Park and Forest Service) began an EU-funded project called Hydrology LIFE. The project aims to safeguard not just mires, but also small water bodies and important bird lakes in 103 Natura 2000 areas. The project restores and protects mires.

Wetland ecology group_University of Helsinki_duck_mire_restoration_hydrology

Mire hydrology can be restored by blocking ditches.

Hydrology is the most important issue to consider when restoring a mire. Blocking ditches leads to changes in water balance, and eventually to active peat formation, which is basically the definition of a mire. After the ditches are blocked, water levels normally rise rapidly to correspond with the natural situation. However, actual peatland processes return at a much slower speed. Forest vegetation is slowly replaced by mire vegetation, starting from the ditches. The processes take a long time, so whether or not the original mire ecosystem returns is yet to be seen. It is also possible that we are actually just creating new mire types.

Wetland ecology group_University of Helsinki_Elimyssalo_mire_peatland_forest reindeer

Elimyssalo nature conservation area in Eastern Finland consists of various peatland types. The area is an important calving place for wild forest reindeer (Rangifer tarandus fennicus).

Helping forest grouse

Wetland ecology group_University of Helsinki_hazel grouse

Forest grouse utilize peatland-forest ecotones. The hazel grouse (Tetrastes bonasia) population in Finland has suffered from peatland loss.

Peatland-forest ecotones are key environments for forest grouse, but unfortunately these areas are becoming very rare. The willow ptarmigan (Lagopus lagopus) has suffered from mire fragmentation in Finland. Ptarmigan habitats are fragmented especially in Southern Finland, and thus there are small populations living far from each other. Luckily, local people are usually interested in peatland restoration that helps species such as the willow ptarmigan. Several good examples exist of how ptarmigans have accepted restored peatlands. The Finnish Association for Nature Conservation has a project “SuoMaa”, which began in 2016, and targets protecting and restoring taiga nature. One of the aims is to restore peatlands to support and enlarge a ptarmigan breeding peatland network and create connections between strong and threatened populations.

 

Read more

Hydrologia-Life

Suomen metsäkanalintukantojen hoitosuunnitelma

Restoration of peatlands, Luke

 

Wetlands, the Earth’s kidneys

Wetlands are one of the world’s most important ecosystems. They are referred to as the “Earth’s kidneys” and that comparison could not be more accurate. Wetlands truly are as important to the planet as kidneys are to humans, with one exception: humans can survive with only one kidney, but the Earth cannot.

Kidneys are in charge of humans’ fluid balance. If we are dehydrated, our kidneys try to preserve as much water in our bodies as possible, and when we have excess water our bodies, our kidneys work to discharge the extra water. Wetlands work in the same way. They mitigate both floods and droughts by absorbing and recharging water.

A wetland photographed from a drone. © Antti Nykänen

In addition to fluid balance, kidneys are also responsible for removing unnecessary and hazardous substances, such as waste products and medical substances. In resemblance to our kidneys, wetlands purify our natural waters. They filter and remove nutrients and pollutants from our rain and floodwaters. Extra nutrients will sink to the bottom of the wetland and hence are available for wetland vegetation. Kidneys purify 1750 litres of blood every day, but the water purification ability of global wetlands is 30-fold. Wetlands purify 30 cubic litres of water daily.

Unfortunately, the world has lost approximately half of its wetlands, and Europe alone has destroyed and altered two-thirds of its wetlands. We need strong actions to retain the Earth’s functioning.

The value of wetlands is essential in urban environments, where nutrient and pollutant levels are manyfold compared to more natural environments. Urban wetlands should be seen as important and cheap tools to purify our stormwaters, along with maintaining biodiversity within cities.

A Moorhen (Gallinula chloropus) chick at a wetland in Finland. © Mia Vehkaoja

Luckily, the Ramsar Convention has acknowledged the importance of urban wetlands and themed this year’s World Wetland Day as “Wetlands for a Sustainable Urban Future”. Happy World Wetland Day 2018! Let’s appreciate the Earth’s vital organs.

Whooper swans don’t out-graze wigeons

A few decades ago the whoopers swan (Cygnus cygnus) was an endangered and rare species in Finland. It only bred in remote lakes and people rarely saw them. The population increase of whooper swans after protection is one of the success stories in Finnish nature conservation. Nowadays the swans can be heard gaggling all around Finland. The whooper swan is a large bird, and it thus consumes a lot of vegetation. Water horsetail (Equisetum fluviatile) is one of its favourites.

The whooper swan population has increased greatly, and their gaggling can be heard widely in Finland.

Certain other species also prefer water horsetails. For example, wigeon (Mareca penelope) broods forage within the horsetail growths searching for emerging invertebrates. A study published earlier this year showed that the water horsetail is disappearing from Finnish and Swedish lakes. The reasons for this pattern are unknown, but one possible explanation could be increased grazing pressure. Whooper swans effectively utilize horsetails, and swan grazing was therefore suspected to be influencing the disappearance of the horsetail. Wigeon populations have concurrently shown a worrying decrease.

A recently published study conducted of 60 Finnish and Swedish lakes utilized vegetation and waterbird data gathered in the early 1990s and in 2016. The study area widely covers the boreal, reaching from southern Sweden to Finnish Lapland. The whooper swan population increased strongly during the study period. Researchers studied whether whooper swans’ grazing on water horsetail is causing the negative trend in the wigeon population. Pair counts were used to indicate waterbird communities, and thus any changes caused during the brood time were not shown.

Whooper swans are grazers that have to consume a great deal of vegetation to survive.

The study showed that whooper swans strongly preferred lakes with horsetails during the 1990s, but this connections is not seen anymore. While the number of swan-occupied lakes has increased, the number of horsetail lakes has decreased dramatically. However, it appears that swans and disappearing horsetails do not associate, because the horsetail has also been from lakes where swans don’t occur. The horsetail has increased in some swan-occupied lakes.

The number of lakes used by wigeon has decreased, but swans are apparently not causing this. Wigeon loss has not been stronger on lakes occupied by swans. Quite the opposite, as wigeons and swans appear to positively correlate. Even though wigeons prefer horsetail lakes, their disappearance is not associated with the horsetail loss occurring in the study lakes, which suggests that wigeons can also utilize other lake types. On the other hand, the researchers note that this study  did not considered the critical brood time, when the foraging opportunities among the horsetail growths are especially important. Thus it may still be possible that wigeons are affected by horsetail loss, but this effect only appears during the brood time.

Read more:

Pöysä et al. 2017. Recovering Whooper Swans do not cause a decline in Eurasian Wigeon via their grazing impact on habitat. Journal of Ornithology.

Pöysä et al. 2017. Habitat associations and habitat change: seeking explanation for population decline in breeding Eurasian wigeon Anas penelope. Hydrobiologia.

Blog text: Vanishing wigeons and fading horsetails

Traffic flattens billions of frogs every year

Amphibians are run over by cars more often than other vertebrates. Per road kilometer, an average 250 amphibian individuals die every year because of traffic. According to this calculation, over 113.5 million frogs die annually on the Finnish road network (454 000 km). In Brazil, one of the world’s amphibian hot spots, traffic annually kills 9 420 frogs on each road kilometer. This means a total of over 16 billion frogs lost due to traffic.

 

Roads built near wetlands are the most significant cause of frog mortality on all continents, but particularly in Europe. No relief is in sight for this problem, because traffic amounts are increasing every year throughout the world.

 

Fast-moving frog species are somewhat fortunate because their traffic mortality is quite low on roads with little traffic (24–40 cars per hour). Up to 94% of fast-moving frogs survive when crossing a road. Slow-moving species, such as the common toad (Bufo bufo), are not that lucky. Only half of common toads survive to the other side of a road. On busier roads (60 cars in an hour) over 90% of common toads are run over by a car.

A dead common toad (Bufo bufo) hit by a car. © Mia Vehkaoja

Amphibians suffer from both direct and indirect negative effects of road networks and traffic. Mortality is a direct cause, whereas isolation is an indirect cause. Amphibians migrate according to seasons: during spring to their breeding grounds and during autumn to their wintering grounds. These migrations make amphibians vulnerable to traffic mortality. Season migrations occur particularly in the temperate zone, such as in Europe, where traffic has become the greatest threat to amphibian survival in certain places.

 

The traffic mortality of frogs decreases population sizes and reduces migration, which lead to a decreasing gene flow between populations and the disappearance of genetic diversity. Smaller populations are at greater risk of going extinct.

 

Historically thousands of kilometers of roads have been built through wetlands, which leads to the disappearance, isolation and depletion of wetland habitats. Roads also influence the cycle and function of water systems. Road construction has drained and polluted wetlands all over the world.

 

Conservation actions should concentrate not only on restricting road construction laws and regulations, but on preventing frogs from accessing roads by installing culverts and fences. According to a French study, the combination of culverts and fences is the most efficient way for saving frogs from traffic mortality. But this is just one study, and unfortunately we still know too little about which methods are best for amphibian conservation.

Four reasons why beaver wetlands are paradise for pin lichens

Beaver activity enhances the occurrence and diversity of pin lichens (Caliciales). Both the number of species and individuals is much higher in beaver-created wetlands than in other types of boreal forest landscapes. There are four reasons behind this:

1. High amounts of deadwood. Pin lichens grow on both living trees and deadwood. Decorticated deadwood in particular is preferred by pin lichens. Beaver-induced flooding kills trees in the riparian zone and produces high amounts of decorticated snags.

Pin lichen on decorticated stump. © Mia Vehkaoja

2. Diversity of deadwood types. Beaver activity produces snags, logs and stumps. Snags are created by the flood, whereas logs and stumps are also produced by beaver gnawing. The diversity of deadwood tree species is also wide, containing both deciduous and coniferous tree species. The diversity of deadwood types maintains a high diversity of pin lichen species.

3. High humidity conditions. High humidity conditions are favorable for many pin lichen species. Old-growth forests are usually the only places in the boreal forest belt that contain high humidity conditions. There the shading of trees creates a beneficial microclimate for pin lichens. Lighting, on the other hand, becomes a limiting factor for pin lichens in old-growth forests. Most snags in beaver wetlands stand in water, where steady and continuously humid conditions are maintained on the deadwood surface.

Snags produced by a beaver flood in Evo (southern Finland). © Mia Vehkaoja

4. Sufficient lighting conditions. Because most of the deadwood in beaver wetlands stands in water, it is concurrently in a very open and sunny environment. Many boreal pin lichens are believed to be cheimophotophytic (cheimoon=winter), meaning that they are able to maintain photosynthesis also during winter at very low temperatures. The algae member of pin lichens requires enough light for photosynthesis. Open beaver wetlands make photosynthesis possible for pin lichens during both summer and winter. Snow also enhances light availability during winter.

More information: Vehkaoja, M., Nummi, P., Rikkinen, J. 2016: Beavers promote calicioid diversity in boreal forest landscapes. Biodiversity and Conservation. 26 (3): 579-591.

It walks and quacks like a mallard, but does it look like one?

This is a mallard (Anas platyrhynchos). It is your basic duck, familiar from park wetlands. A mallard quack is also the classic duck sound.

Wetland ecology group_University of Helsinki_duck_mallard

A wintering mallard flock is quite colourful: males have green heads with yellow beaks and both sexes have blue wing spots.

Age and season affect plumages

But mallards do not always look like those in the picture above. Males do not always have green heads, nor are females always brownish grey. Depending on the season, and the age and genes of an individual, mallards can look a little different. Downy ducklings resemble the ducklings of all other dabbling duck species. However, they rapidly develop species-specific characters, and young drakes for example develop a hint of green on their head even before all the down has disappeared. In the summertime males briefly change into summer (eclipse) plumage that looks like female plumage. Except that a male beak is still yellow.

Wetland ecology group_University of Helsinki_duck_mallard male_sinisorsa

A young male mallard still has down on his back, while some green is already glittering on his head. Both female and male mallards are brown during summer and autumn. The yellow beak reveals that this individual is a male. © Sari Holopainen

Beak reveals sex

In addition to normal changes in plumages caused by seasons or growth, weird looking mallards can also be found. Their plumages might be different due to changes in their genes or hormones.

Wetland ecology group_University of Helsinki_duck_mallard female_sinisorsa

Light female mallard.

Various phenotypes are rather typical among animal species. These variations are common in mallards, and peculiar individuals can be found especially in cities. For example, females might be light due to mutations. Mutations can work in several ways causing changes in pigment production or in its appearance traits. Lightly coloured mallards produce pigments, but their colour appearance has changed. If an individual does not produce melanin pigments at all, it becomes a completely white albino.

Colour variations are thought to be typical in mallards in city environments, where predator pressure is lower and thus exceptional individuals survive better. On the other hand, mallard farming has potentially produced weird-looking individuals that have escaped and spread their genes to natural populations.

Wetland ecology group_University of Helsinki_duck_mallard_intersexual

Wetland ecology group_University of Helsinki_duck_mallard_intersexual_male_female

These peculiar mallard males in wintering flocks are actually females. The pictures show intersexual females together with two normal males and a female. Moulting males changing their eclipse plumage into nuptial plumage can look similar, but their beak colour once again reveals the actual sex. These pictures were also taken in the middle of winter, when males have already changed to their nuptial plumage.

The beak has an important role in identifying mallard sexes because males have yellow beaks and females have orange-spotted beaks around the year. The beak can also reveal intersexual females. They are individuals that express both female and male outfit. This can be caused by disturbances in female hormone production, or then an individual has both female and male features. Hormones regulate the outfit, and if large quantities of testosterone are produced, male plumage may result. Beak colouration is not as sensitive to hormonal changes and even though a female displays male characteristics, it will still have a female beak.

Hybrid ducks

Wetland ecology group_University of Helsinki_duck_mallard_teal_sinisorsa_tavi

This common teal x mallard hybrid male was coupled with a normal mallard female and defended it against clearly larger mallard males.

Mallard flocks may also have hybrid individuals. Duck species are close relatives, and can thus mix rather easily. Various species mixes are known, for example mallards can mix with common teals, Eurasian wigeons, northern pintails and black ducks. However, hybrids are quite rare, because each duck species have specific behaviours and characteristics that prevent hybridization. But sometimes these barriers collapse, and hybrid individuals are born. Hybrid individuals express characteristics from both original species. Their habits and characteristics typically do not interest individuals from the original species and therefore might not breed successfully.

Hybridization can cause several problems, which in the worst-case scenario can lead to the extinction of the original species. The hybridizations of mallard and black ducks in North America is becoming more common after shifts in their distribution. Hybridization is now threating black duck populations. Alien mallards can also cause a serious risk for endemic duck species and to their gene pool. For example, the Hawaiian duck (Anas wyvilliana) is unfortunately going extinct because of non-native mallards. Survival of the species now depends on protection actions that target the extirpation of all mallards and hybrids from the islands

Wetland ecology group_University of Helsinki_duck_mallard_intersexual_male_female_sinisorsa

Four naturally different mallards wintering in southern Finland. The normal type male was coupled with a normal female. An intersexual and a light female are in the upper part of the picture.

It looks like a duck

This white domestic duck is a descendant of a mallard. © Sari Holopainen

This white domestic duck is a descendant of a mallard. © Sari Holopainen

Mallards are commonly farmed, and several different colour variations exist among the domestic breeds. A white duck known by everyone is also a mallard variant. Farmed mallards have sometimes escaped, and now breed with natural mallards. Extraordinary ducks, resembling mallards more or less, are a fairly common sight in Southern and Central European parks. Alien genes in the natural mallard population become more rare in the northern parts of Europe.

Extraordinary ducks in European parks are probably related to mallards: Switzerland, Germany and Sweden. © Sari Holopainen

Extraordinary ducks in European parks are probably related to mallards: Switzerland, Germany and Sweden. © Sari Holopainen

Read more:

Pär Söderquist: Large-Scale Releases of Native Species: the Mallard as a Predictive Model System

Pictures by Harry J. Lehto, intersexual mallards

Pictures by Pekka Sarvela, colour variations

Ducks Unlimited: Waterfowl Hybrids