Foraging behaviour of the Eurasian Three-toed Woodpecker Picoides tridactylus in its peak abundance after wildfire

In the boreal biome, forest fires are the most important natural disturbance influencing tree substrate availability and quality for a range of specialized species. This includes the Eurasian Three-toed Woodpecker Picoides tridactylus, which is known to promptly utilize burned forest habitats. However, there are no studies addressing the foraging behaviour of this woodpecker in forests affected by wildfire. Such knowledge could assist the development of efficient post-fire management strategies which are in line with biodiversity conservation objectives. This study describes the foraging behaviour of the Eurasian Three-toed Woodpecker during the breeding season in a forest area of 13,100 ha in southcentral Sweden affected by a major wildfire in 2014. During the second breeding season after fire, we used instantaneous sampling where we observed the foraging behaviour of 28 individuals during a total of 1681 observation minutes. Our results suggest that Norway Spruce Picea abies and larger diameter trees (DBH > 25 cm) are important foraging substrates. However, data on time spent foraging on the different substrates suggest that Scots Pines Pinus sylvestris also are important. In particular, we identified the importance of the root collars, where excavation into sapwood was the main foraging method. Our study was performed during a clearly visible peak of Eurasian Three-toed Woodpecker abundance and this may suggest that the level of food resources available was very high which led to observed foraging patterns not necessarily observed in other types of habitats.Peer reviewe

Ecological Restoration of the Boreal Forest in Fennoscandia

Mixed-severity disturbances have historically shaped boreal forests, creating a dynamic mosaic landscape. In Fennoscandia, however, intensive even-aged forest management has simplified the forest landscape, threatening biodiversity. To safeguard this biodiversity, we therefore need to restore structural complexity in hitherto managed forests. Knowledge generated from relevant case studies on natural disturbance emulation–based ecological restoration suggests that prescribed burning positively affects many early-successional organisms. Gap cutting benefits some insects and wood fungi but has a limited effect on birds, bryophytes, and vascular plants. Restoration of deciduous forests appears to benefit light- and deciduous tree–associated insect species and some forest birds

Ecological barriers mediate spatiotemporal shifts of bird communities at a continental scale

This study was supported by the Swiss National Science Foundation (grant P2BEP3_195232) and by the Academy of Finland (project 323527 and project 329251).Species' range shifts and local extinctions caused by climate change lead to community composition changes. At large spatial scales, ecological barriers, such as biome boundaries, coastlines, and elevation, can influence a community's ability to shift in response to climate change. Yet, ecological barriers are rarely considered in climate change studies, potentially hindering predictions of biodiversity shifts. We used data from two consecutive European breeding bird atlases to calculate the geographic distance and direction between communities in the 1980s and their compositional best match in the 2010s and modeled their response to barriers. The ecological barriers affected both the distance and direction of bird community composition shifts, with coastlines and elevation having the strongest influence. Our results underscore the relevance of combining ecological barriers and community shift projections for identifying the forces hindering community adjustments under global change. Notably, due to (macro)ecological barriers, communities are not able to track their climatic niches, which may lead to drastic changes, and potential losses, in community compositions in the future.Publisher PDFPeer reviewe

Emulating natural disturbances for the conservation of boreal forest birds

In the boreal biome, intensive forestry and fire suppression have led to the loss of natural disturbances regimes and changes in forest ecosystems at the landscape and local scale. A large proportion of the old-growth forests has been converted into even-aged single-species forests, with degraded understory layer and reduced availability of dead wood. This has resulted in the population decline of bird species that rely on structurally complex forest habitat. Restoring habitat structures by mimicking natural disturbance regimes can help to safeguard biodiversity. In this study I evaluated the effects of two ecological restoration measures – prescribed burning and gap cutting – on bird assemblage structure and breeding performance of the European pied flycatcher Ficedula hypoleuca in boreal forests. Additionally, I identified biodiversity indicators and tested how ecological restoration can affect their indicator value. Lastly, I characterized substrate preferences and foraging behavior as measured through foraging time of the Eurasian three-toed woodpecker Picoides tridactylus in forest stands subjected to prescribed burning and in unburned forests. Prescribed burning increased the abundance of long-distance migrants, ground breeders, strong cavity excavators and species preferring early-successional habitat. Furthermore, fire had positive effects on the body condition of nestlings of pied flycatchers, this suggest that local habitat quality improved. Gap cutting did not influence bird assemblage structures neither the reproductive output nor nestling body condition. The three-toed woodpecker and the Siberian jay Perisoreus infaustus were identified as potential biodiversity indicators among birds. However, after fire, the goldcrest Regulus regulus became the best predictor of high species richness. The main foraging substrate for three-toed woodpeckers can be characterized as freshly dead trees with a diameter breast height (DBH) of more than 15 cm. However, data on foraging behavior suggest that substrates in the 5-15 cm DBH range and living trees are important as well. The main conclusion from this study is that prescribed burning as a restoration treatment is an effective way to restore habitat for boreal forest birds in managed boreal forest landscapes. These results should encourage forest managers to reintroduce more fire in boreal forests as a complement to other conservation measures

The three-toed woodpecker: an important biodiversity indicator and model species for the conservation of biodiversity in boreal forests.

The use of biodiversity indicators have been proposed as a comprehensive method for assessing conservation values at the stand scale. In the boreal biome, the three-toed woodpecker have been proposed as an indicator for high species richness of co-occurring forest birds. However, to be able to fully understand the potential of biodiversity indicators it is necessary to understand when indicators are valid indicators, as natural dynamics within boreal forest systems can effect bird communities and thus indicator values of species. To assess the impact of natural disturbances we collected data within a large-scale field experiment where we assessed the short term (4-5 years) impact of two restoration treatments mimicking natural disturbances − prescribed burning (n=10) and gap cutting (n=10), using continuous cover stands (n=20) as references − on boreal breeding bird assemblages. We performed detailed bird inventories, through territory mapping and additionally we collected data of local stand characteristics. In this study, we confirmed that the three-toed woodpecker belong to the best indicators of high species richness and abundance within resident forest birds occurring in middle and northern boreal forests. However, the three-toed woodpecker lost its indicator value after prescribed burning; in these stands the goldcrest was the best biodiversity indicator. Based on habitat associations we found that the three-toed woodpeckers is closely associated with structural complexity within forest stands, similar to co-occurring species. Thus structural complexity at such may influence species richness. Still the three-toed woodpecker can be used for conservation planning if their habitats/resource requirements are set as quantitative targets. To accommodate managers with management recommendation regarding these quantitative targets, we quantified refined habitat thresholds and related this with their foraging substrate selection. We found resource requirement thresholds by a 0.9 probability of occurrence of 1.5 m2/ha freshly dead spruce and 0.07 m2/ha dying spruce. By focal bird observations we were able to confirm that indeed modeled resources matched with important foraging substrates for three-toed woodpecker in mature forest areas. This suggest that proposed resource thresholds can be used to plan forest management concerning three-toed woodpeckers population. However, we need to consider additional habitat structures when we planning forest management aiming to conserve biodiversity.peerReviewe

Comparing the effects of even-aged thinning and selective felling on boreal forest birds

Biodiversity is in decline and therefore alternative forest management approaches have gained interest. One of such approaches is uneven-aged silviculture, which has been suggested to better maintain mature or late-successional forest characteristics and species assemblages than even-aged silviculture. Therefore, it is assumed that uneven-aged silviculture can be a useful tool for landscape planning to benefit biodiversity. Nevertheless, there is a lack of empirical studies regarding bird responses to uneven-aged silviculture in north European boreal ecosystems. Here we test the similarity of bird assemblage structure between mature forests within even-aged silviculture (‘thinning’) and uneven-aged silviculture (‘selective felling’). In spring 2018 we censused breeding birds using territory mapping in 14 thinned stands and 14 selectively felled stands. We found higher abundance and different bird assemblages in thinned stands compared to selectively felled stands. The pied flycatcher, tree pipit and great tit contributed most to the variation of bird assemblages between the two management types. None of the species were more abundant in selectively felled than in thinned stands. According to functional guilds, the abundance of ground breeders, ground feeders and generalists was higher in thinned stands than in selectively felled stands, similar results were found in the species richness of long-distance migrants, ground nesters, secondary cavity nesters and generalists. Independent of management type, time since treatment had an overall effect on assemblage structures, the mistle thrush and wren were negatively correlated with time since treatment, while the chiffchaff showed the opposite trend. Our results suggest that at these locations and given this particular type of uneven-age management, selective felling is less suitable for some abundant generalists than even-aged forest stands reaching the thinning age. However, the results from this study does not provide clear management recommendations aiming to maintain biodiversity, as management guidelines should be based on red-listed species and not on common generalists. Nevertheless, our results stresses the urgent need for more long-term studies comparing the effect of these different silvicultural strategies on bird assemblages. © 2020 The Author(s

Foraging behavior of the Eurasian three-toed woodpecker (Picoides tridactylus) and its implications for ecological restoration and sustainable boreal forest management

Several studies have shown that the Three-toed Woodpecker (Picoides tridactylus) is strongly favored by large-scale disturbances, including forest fires. However, natural disturbances have largely disappeared from European boreal forests because of modern forestry practices and fire suppression. We currently lack knowledge on the foraging activity and resource use of the Eurasian Three-toed Woodpecker, especially in burned forests, and this restricts our ability to develop strategies for sustainable forest management and ecological restoration aiming at improving the situation of this woodpecker and associated species. In order to fill this knowledge gap, we studied the characteristics of selected foraging substrates and the foraging behavior of the Three-toed Woodpecker during the breeding season in unburned forests and forests that have been subjected to prescribed burning. We used instantaneous sampling duringtwo consecutive springs (2016-2017), where we observed the woodpeckers’ foraging behavior during a total of 977 minutes in burned forest and 962 minutes in unburned forests. The preferred foraging substrate for Three-toed Woodpeckers in both burned and unburned forests can be characterized as freshly dead trees with a DBH > 15 cm. However, data on time spent foraging on different substrates suggest that also substrates in the 5-15 DBH range and living trees are important. Additionally, prescribed burnings led to less pronounced selection of tree species, which suggest that fire may reduce differences in abundance of saproxylic insect prey between tree species. This information on substrate selection and foraging time provide complementary knowledge and thus should be used simultaneously when management strategies for improved woodpecker habitat are developed. Our results suggest that both prescribed burning and protecting forests with high density and diversity of dead wood provides habitat opportunities for Three-toed Woodpeckers and using both in management may maximize conservation outcom

Foraging behavior of the Eurasian Three-toed Woodpecker (Picoides tridactylus) and its implications for ecological restoration and sustainable boreal forest management

Several studies have shown that the Three-toed Woodpecker (Picoides tridactylus) is strongly favored by large-scale disturbances, including forest fires. However, natural disturbances have largely disappeared from European boreal forests because of modern forestry practices and fire suppression. We currently lack knowledge on the foraging activity and resource use of the Eurasian Three-toed Woodpecker, especially in burned forests, and this restricts our ability to develop strategies for sustainable forest management and ecological restoration aiming at improving the situation of this woodpecker and associated species. In order to fill this knowledge gap, we studied the characteristics of selected foraging substrates and the foraging behavior of the Three-toed Woodpecker during the breeding season in unburned forests and forests that have been subjected to prescribed burning. We used instantaneous sampling during two consecutive springs (2016-2017), where we observed the woodpeckers' foraging behavior during a total of 977 minutes in burned forest and 962 minutes in unburned forests. The preferred foraging substrate for Three-toed Woodpeckers in both burned and unburned forests can be characterized as freshly dead trees with a DBH > 15 cm. However, data on time spent foraging on different substrates suggest that also substrates in the 5-15 DBH range and living trees are important. Additionally, prescribed burnings led to less pronounced selection of tree species, which suggest that fire may reduce differences in abundance of saproxylic insect prey between tree species. This information on substrate selection and foraging time provide complementary knowledge and thus should be used simultaneously when management strategies for improved woodpecker habitat are developed. Our results suggest that both prescribed burning and protecting forests with high density and diversity of dead wood provides habitat opportunities for Three-toed Woodpeckers and using both in management may maximize conservation outcome

Experimental evidence shows the importance of behavioural plasticity and body size under competition in waterfowl

When differently sized species feed on the same resources, interference competition may occur, which may negatively affect their food intake rate. It is expected that competition between species also alters behaviour and feeding patch selection. To assess these changes in behaviour and patch selection, we the functional response for each species and then recorded their behaviour and patch selection with and without potential competitors, using different species combinations. Our results showed that all three species acquired the highest nitrogen intake at relatively tall swards (6, 9 cm) when foraging in single species flocks in the functional response experiment. Goose species were offered foraging patches differing in sward height with and without competitors, and we applied an experimental approach using captive birds of three differently sized Anatidae species: wigeon (Anas penelope) (∼600 g), swan goose (Anser cygnoides) (∼2700 g) and bean goose (Anser fabalis) (∼3200 g). We quantified tested for the effect of competition on foraging behaviour. The mean percentage of time spent feeding and being vigilant did not change under competition for all species. However, all species utilized strategies that increased their peck rate on patches across different sward heights, resulting in the same instantaneous and nitrogen intake rate. Our results suggest that variation in peck rate over different swards height permits Anatidae herbivores to compensate for the loss of intake under competition, illustrating the importance of behavioural plasticity in heterogeneous environments when competing with other species for resources

Ecological restoration for biodiversity conservation triggers response of bark beetle pests and their natural predators

The restoration of forest structure and function is increasingly being used in boreal forests in order to halt the loss of biodiversity. Often ecological restoration is aimed at increasing the volume of dead and dying trees to enhance the biodiversity of deadwood-dependent organisms, but it may also increase population sizes of pest bark beetle species, even several years following restoration. Herein, we used a large-scale restoration experiment in Northern Sweden to assess the 5 years post-restoration effects of restorative gap cutting and prescribed burning on the populations of a set of economically harmful pest bark beetles (Ips typographus, Polygraphus poligraphus, Tomicus piniperda and Pityogenes chalcographus) and the most important predators of bark beetles, Thanasimus spp. In addition, we assessed the effects of forest stand characteristics at stand and landscape scale on the abundance of I. typographus. Five years post-restoration, gap-cut stands supported the highest abundances of P. poligraphus and contained the highest count of spruce trees newly attacked by bark beetles. By contrast, prescribed burning generally sustained the lowest abundances of pest bark beetles, especially I. typographus and P. poligraphus, and the highest abundance of their natural predators Thanasimus spp. The population abundance of I. typographus was also positively affected by the area of clear cuts within a 500 m radius from the stand. In conclusion, prescribed burning appears to be a safer method for ecological restoration than gap cutting in the long-term. According to our results, a risk of a local bark beetle outbreak still remains 5 years following the initiation of ecological restoration treatments on spruce-dominated mature gap-cut stands