Monitoring is essential in conservation biology for assessing a species' population status and development. Many broad-scale programs rely on citizen science approaches but surveying rare or elusive species often requires specific training for volunteers. The Lesser Spotted Woodpecker Dryobates minor is an indicator of healthy forest ecosystems, particularly structurally rich deciduous and riparian forests. The species is difficult to observe due to its elusive behaviour, making reliable information about population status and habitat requirements scarce. Recognizing this critical data gap, a citizen science project was initiated in Hesse and Bavaria, Central and Southern Germany. The project, integrated into the national monitoring of rare breeding birds, trained volunteers to systematically map this species. Monitoring was conducted from 2021 to 2024 along 187 monitoring transects using playbacks to lure woodpeckers and the NaturaList app to record observations. Additionally, habitat data, such as the number of dead trees, proximity to water bodies and habitat type, were collected. Cavity cameras were used to monitor active breeding cavities. Lesser Spotted Woodpeckers were detected during 323 of 1012 surveys (32%), with detection probability peaking in March. The prior bird knowledge of the citizen scientists positively influenced detection probability. Species occurrence probability was highest in deciduous, riparian, and mixed forests characterized by large amounts of standing dead trees. Nest survival was 74%, with 1.8 fledglings per brood on average. Predators included Great Spotted Woodpeckers Dendrocopos major, and Garden Dormice Eliomys quercinus. Nest survival increased with the number of standing dead trees in the vicinity of breeding cavities. These findings emphasize the importance of deciduous forests and standing deadwood in supporting the species' occurrence and nest survival and highlights the value of citizen science as powerful tool for generating large-scale data, enabling more effective long-term monitoring of elusive species.

We investigated variation in home range size of the White-backed Woodpecker Dendrocopos leucotos, a species dependent on old-growth structures, in Central European forests varying in management intensity. Specifically, we used data from woodpeckers radio-tracked between 2016 and 2019 to test predictions of three hypotheses proposed to explain variation in home range size. Mean (± SD) 95% home range size calculated with fixed kernel density estimation was 22 ± 11 ha (N = 27) in the breeding season (» April and May) and 47 ± 27 ha (N = 28) in the post-breeding season (» June and July). Home ranges of neighboring individuals overlapped neither in the breeding season nor in the post-breeding season, suggesting territoriality in both seasons. The resource distribution and intraspecific competition hypotheses were supported during the breeding season, whereas neither hypothesis explained post-breeding home range size. Breeding home range size decreased with both increasing forest area in the landscape and increasing proportion of resource-rich habitat (snag volume and trees with dead branches), the latter being particularly relevant when forest area was low. Moreover, breeding home range size decreased with increasing population density when the proportion of resource-rich habitat was high. The mechanisms determining breeding home range size thus varied with habitat quality in the landscape. In regions with low forest area and presumably generally low habitat quality, home range size appeared to be influenced by the distribution of resources. By contrast, in regions with high resource abundance and high population density, home range size seemed to be regulated by intraspecific competition. To improve habitat quality, deadwood and old trees should ideally be clumped within stands with little or no forest management. These resource-rich forests should constitute a high proportion of areas at least the size of a breeding home range and are particularly important in little-forested regions.

Long-term studies provide solid frameworks for addressing key questions in ecology and conservation. First, they allow collecting high amounts of data necessary to assess data-hungry hypotheses. Second, long-term studies allow testing hypotheses that require long time series. Third, they serve as sentinel systems to investigate the effects of sudden environmental changes (e.g., wildfires, floodings, severe droughts). Using the experience on a long-term study (2000-present) of Middle Spotted Woodpeckers Dendrocoptes medius in NW Spain, I identify and propose some approaches for addressing a set of key questions. Long-term studies are essential to investigate lifetime fitness performance of floating adults, which strongly influence population persistence of woodpeckers and many other organisms. A second data-hungry question is related to the factors that influence the use of habitat patches as stepping stones for dispersing juveniles and floaters. Long-term time series are also necessary to investigate population persistence under climate and habitat changes. Moreover, long-term data on woodpecker reproduction and cavity occupancy by secondary cavity users will help understanding the role of woodpeckers as indicators and keystone ecosystem engineers, and will unravel the mechanisms underlying nest-site selection in primary cavity nesters. Finally, woodpeckers´ habitat specialization provides a suitable framework to investigate the drivers of foraging habitat quality in birds. Despite the relevance of long-term woodpecker studies for the generation of robust knowledge, most funding programmes do not promote, or even penalize, studies on these species because they require long periods. This issue biases our knowledge towards model species and systems comparatively easy to study in short periods.

The Great Slaty Woodpecker Mulleripicus pulverulentus (GSWO), one of the world's largest, occurs in mature broadleaved forests of south- and southeast Asia. Habitat loss, logging, and timber extraction has caused a drastic population decline, due to which it is listed 'vulnerable' by IUCN. Despite its threatened status, basic knowledge about its breeding biology is deficient. We studied the nesting ecology of the GSWO in the Himalayan foothill Sal Shorea robusta dominated dipterocarp forests of Uttarakhand, northwest India over four years (2016–2019). We searched for active GSWO nests and documented various aspects of nesting from cavity excavation to fledging. Data were collected using direct observations by observers, as well as by video footage of active nests by cavity cameras and time-lapse cameras. We observed 9 nesting instances from 5 nesting cavities. All cavities were excavated in live Sal trees of DBH 53–98 cm (mean 73.4 cm). Nest excavation took a minimum of 9 days. Clutch size was 4, wherein one egg was laid per day over 4 successive days. Incubation period was 12–13 days. The number of chicks successfully fledged was generally 2 (range 1–3). Fledging duration was 5–6 weeks. Cooperative breeding was confirmed at 6 out of 9 nests, with 1–3 regular helpers (accompanied by 1–2 additional individuals) assisting the active pair in care of the young. Care duties were primarily shared between male and female adults, with minor/passive contribution by helpers. We documented instances of reuse of nest cavities across years by GSWO. We recorded predation on GSWO chicks by Bengal Monitor Varanus bengalensis lizards and Yellow-throated Marten Martes flavigula. Breeding success was 67%. Information generated during our study about the breeding ecology of the GSWO contributes towards a better understanding of the species and will aid to guide conservation actions targeted at this threatened woodpecker.

Woodpeckers represent a frequent component of mixed-species flocks in subtropical forests but have received less attention in mixed flock research than Passeriformes and other bird taxa. To understand when and how woodpeckers join this type of association and their role within them, we surveyed mixed flocks for 388hs over three years in Argentina's Yungas foothill forest. We studied the association frequency and foraging behavior inside and outside mixed flocks of the four woodpecker species present in the study area: Cream-backed Woodpecker Campephilus leucopogon, Golden-olive Woodpecker Colaptes rubiginosus, Dot-fronted Woodpecker Veniliornis frontalis, and White-barred Piculet Picumnus cirratus. Woodpeckers were present in 26% of the 206 recorded mixed flocks, with a higher frequency during dry seasons. They joined mixed flocks with twice as many species as the average flock in the area and shared the flock with other non-woodpecker bark-forager species in 88% of cases. The largest species, Cream-backed Woodpecker, joined flocks less often than smaller species but frequently participated in flocks composed mainly of other large-sized bird species. We recorded the foraging behavior of 52 woodpecker individuals for durations ranging from 11 to 449 seconds: 24 within mixed flocks and 28 outside. Some woodpecker species were found to mimic other bark-forager species' foraging sites in an exact manner. Medium-sized species foraged higher when inside mixed flocks, whereas the largest and smallest species did not alter their foraging height. Only the smallest species, White-barred Piculet, increased its foraging efficiency within mixed flocks and was recorded as a leader in understory flocks. Further insights are needed into the disadvantages and/or benefits of woodpecker species joining mixed flocks. However, our results indicate that woodpecker participation in mixed-species flocks is primarily influenced by higher flock diversity and the presence of other non-woodpecker bark-foragers, the latter also playing a key role in enhancing their foraging success.

Inter-specific variation in trends of breeding phenology is well documented across cavity nesting passerines. However, general conclusions about the consistency of phenological shifts across closely related open nesting species are yet to be achieved. We used ringing data from 1960 to 2015 during the nesting season of three Acrocephalus species breeding in syntopy at a single fishpond area, “Bohdanečsko” in the Czech Republic, to test whether long-term trends in the timing of the fledging period coincide among Common Reed A. scirpaceus, Marsh A. palustris, and Sedge A. schoenobaenus Warblers. Using logistic regression, we showed that trends in the fledging period were not fully consistent among the three closely related reed warblers. While the middle phases of the fledging period advanced in all species, the early phases were delayed in A. scirpaceus and A. schoenobaenus. The fledging periods became shorter in all species. The variation observed among these species makes it less likely that a single factor, such as climate warming, is the sole culprit of phenological changes. We suggest that interspecific competition and habitat change may have constrained Acrocephalus warblers from adjusting breeding times to increasing spring temperatures.

Egg size in birds is a crucial fitness trait with high individual consistency. While the causes of this consistency are not fully understood, different sources of egg size variation in birds have been proposed. This study investigated the repeatability of egg size in two south temperate populations of Southern House Wrens Troglodytes musculus bonariae and examined the influence of climatic factors and female traits on egg size. During the 2008–2011 seasons, we measured the length and width of eggs from 296 House Wren clutches and estimated their volume. Our analyses revealed high repeatability of egg size of southern House Wrens within and across breeding seasons, with no differences between study sites. This high repeatability suggests a substantial influence of consistent environmental factors as no evidence of significant heritability was found. However, environmental factors and female traits did contribute to a small portion of the egg size variation. These findings challenge the notion that high additive genetic variance drives the high repeatability of egg size in Southern House Wrens. Instead, our results support the hypothesis that individual female traits play a key role in determining egg size consistency in the species.