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Citizen science is mainstream: millions of people contribute data to a growing array of citizen science projects annually, forming massive datasets that will drive research for years to come. Many citizen science projects implement a \"leaderboard\" framework, ranking the contributions based on number of records or species, encouraging further participation. But is every data point equally \"valuable?\" Citizen scientists collect data with distinct spatial and temporal biases, leading to unfortunate gaps and redundancies, which create statistical and informational problems for downstream analyses. Up to this point, the haphazard structure of the data has been seen as an unfortunate but unchangeable aspect of citizen science data. However, we argue here that this issue can actually be addressed: we provide a very simple, tractable framework that could be adapted by broadscale citizen science projects to allow citizen scientists to optimize the marginal value of their efforts, increasing the overall collective knowledge.

Contrasting trajectories of biodiversity loss and urban expansion make it imperative to understand biodiversity persistence in cities. Size‐, local‐, and landscape‐level habitat factors of greenspaces in cities may be critical for future design and management of urban greenspaces in conserving bird biodiversity. Most current understanding of bird communities in cities has come from disparate analyses of single cities, over relatively short time periods, producing limited understanding of processes and characteristics of bird patterns for improved biodiversity management of the world's cities. We analyzed bird biodiversity in 112 urban greenspaces from 51 cities across eight countries, using eBird, a broadscale citizen science project. Species richness and Shannon diversity were used as response variables, while percent tree cover, percent water cover, and vegetation index were used as habitat predictor variables at both a landscape (5 and 25 km radius) and local‐scale level (specific to an individual greenspace) in the modeling process, retrieved using Google Earth Engine. Area of a greenspace was the most important predictor of bird biodiversity, underlining the critical importance of habitat area as the most important factor for increasing bird biodiversity and mitigating loss from urbanization. Surprisingly, distance from the city center and distance from the coast were not significantly related to bird biodiversity. Landscape‐scale habitat predictors were less related to bird biodiversity than local‐scale habitat predictors. Ultimately, bird biodiversity loss could be mitigated by protecting and developing large greenspaces with varied habitat in the world's cities.

The common myna (Acridotheres tristis) is one of the most invasive bird species in the world, yet its colonisation history is only partly understood. We identified the introduction history and population structure, and quantified the genetic diversity of myna populations from the native range in India and introduced populations in New Zealand, Australia, Fiji, Hawaii, and South Africa, based on thousands of single nucleotide polymorphism markers in 814 individuals. We were able to identify the source population of mynas in several invasive locations: mynas from Fiji and Melbourne, Australia, were likely founded by individuals from a subpopulation in Maharashtra, India, while mynas in Hawaii and South Africa were likely independently founded by individuals from other localities in India. Our findings suggest that New Zealand mynas were founded by individuals from Melbourne, which, in turn, were founded by individuals from Maharashtra. We identified two genetic clusters among New Zealand mynas, divided by New Zealand’s North Island’s axial mountain ranges, confirming previous observations that mountains and thick forests may form barriers to myna dispersal. Our study provides a foundation for other population and invasion genomic studies and provides useful information for the management of this invasive species.

Urbanisation typically results in a reduction of hollow-bearing trees and an increase in the density of particularly species, potentially resulting in an increased level of competition as cavity-nesting species compete for a limited resource. To improve understanding of hollow usage between urban cavity-nesting species in Australia, particularly parrots, we investigated how the hollow-using assemblage, visitation rate, diversity and number of interactions varied between hollows within urban remnant forest and continuous forest. Motion-activated video cameras were installed, via roped access to the canopy, and hollow usage was monitored at 61 hollows over a two-year period. Tree hollows within urban remnants had a significantly different assemblage of visitors to those in continuous forest as well as a higher rate of visitation than hollows within continuous forest, with the rainbow lorikeet making significantly more visitations than any other taxa. Hollows within urban remnants were characterised by significantly higher usage rates and significantly more aggressive interactions than hollows within continuous forest, with parrots responsible for almost all interactions. Within urban remnants, high rates of hollow visitation and both interspecific and intraspecific interactions observed at tree hollows suggest the number of available optimal hollows may be limiting. Understanding the usage of urban remnant hollows by wildlife, as well as the role of parrots as a potential flagship for the conservation of tree-hollows, is vital to prevent a decrease in the diversity of urban fauna, particularly as other less competitive species risk being outcompeted by abundant native species.

Foraging decisions tend to drive individuals toward maximising energetic gains within a patchy environment. This study aims to determine the extent to which rainfall, and associated changes in food availability, can explain foraging decisions within a patchy urbanised landscape, using the Australian white ibis as a model species. Ibis density, food consumption rates and food abundance (both natural and anthropogenic) were recorded during dry and wet weather within urban parks in Sydney, Australia. Rainfall influenced ibis density in these urban parks. Of the four parks assessed, the site with the highest level of anthropogenic food and the lowest abundance of natural food (earthworms), irrespective of weather, was observed to have three times the density of ibis. Rainfall significantly increased the rate of earthworm consumption as well as their relative availability in all sites. Overall, these density and consumption measures indicate that anthropogenic derived foods, mainly from direct feeding by people, explain the apparent distribution of ibis across urban parks. However, there was evidence of prey-switching when the availability of natural foods increased following rainfall, perhaps reflecting selection of particular nutrients.

ContextUrbanization fragments and destroys natural landscapes, generally decreasing bird diversity. While in some cases bird diversity continuously decreases in response to urbanization, in others a non-linear response is evident, with peak bird diversity observed at intermediate levels of urbanization. But many studies previously investigating this pattern are spatially or temporally constrained.ObjectivesIn this study, we analyzed the impacts of urbanization on bird diversity, stratified to native and exotic species. We specifically investigated the differences in bird diversity between natural and urban green areas.MethodsWe used eBird citizen science data (> 4,000,000 bird-survey lists) and remotely-sensed landcover data, throughout the contiguous United States of America.ResultsWe found a non-linear response to urbanization for both species richness and Shannon diversity. There was distinctly greater bird richness and Shannon diversity in urban green areas compared to natural green areas. Our observed response is likely explained by an increase in habitat heterogeneity of urban green areas compared with natural green areas.ConclusionsOur work highlights the importance of diverse urban green areas for supporting bird diversity in urban areas. We recommend that urban planning should focus on maintaining high habitat heterogeneity in urban green areas to promote greater bird diversity.

Controlling problem species for conservation can be fraught, particularly when native species are subject to lethal control. The noisy miner (Manorina melanocephala), has been the target of numerous lethal control efforts. Outcomes of these noisy miner removals have varied substantially, so identifying the circumstances under which they are effective is essential for ethical and effective management. We compiled data for all identified noisy miner removals (n = 45), including both permit‐based and unofficial removals. We investigated whether methodological and ecological factors explained the effectiveness of removals in reducing noisy miner density or increasing woodland bird richness and abundance. The only predictor of any measure of success was time between first and final culls which was positively related to reduction in noisy miner density. Surprisingly, despite removals mainly failing to reduce noisy miner density to below a threshold above which noisy miners impact smaller birds, woodland birds usually still increased. Disrupted social structure as noisy miners recolonized may have led to less effective aggressive exclusion of small birds. Further removals may not need to reduce noisy miner density to below this threshold to benefit woodland birds, but consistent monitoring and reporting would support better evaluation of effectiveness and correlates of success. The outcomes of noisy miner removal initiatives to conserve woodland birds have varied substantially, thus identifying the circumstances under which they are effective is essential for ethical management of this native problematic species. We collected and analyzed data for all known permit‐based and unofficial noisy miner removals to identify whether methodological and ecological factors explained the effectiveness of removals in reducing population sizes and improving richness and abundance of small woodland birds. To benefit small woodland birds, noisy miner density may not need to be reduced to below the threshold at which assemblages are disrupted in unmanaged situations.

We are currently in the midst of Earth's sixth extinction event, and measuring biodiversity trends in space and time is essential for prioritizing limited resources for conservation. At the same time, the scope of the necessary biodiversity monitoring is overwhelming funding for professional scientific monitoring. In response, scientists are increasingly using citizen science data to monitor biodiversity. But citizen science data are ‘noisy’, with redundancies and gaps arising from unstructured human behaviours in space and time. We ask whether the information content of these data can be maximized for the express purpose of trend estimation. We develop and execute a novel framework which assigns every citizen science sampling event a marginal value, derived from the importance of an observation to our understanding of overall population trends. We then make this framework predictive, estimating the expected marginal value of future biodiversity observations. We find that past observations are useful in forecasting where high-value observations will occur in the future. Interestingly, we find high value in both ‘hotspots’, which are frequently sampled locations, and ‘coldspots’, which are areas far from recent sampling, suggesting that an optimal sampling regime balances ‘hotspot’ sampling with a spread across the landscape.

Invasive species threaten native ecosystems, the economy and human health. Improved understanding of an invasive species’ ecological niche, and whether it has differentiated in the invasive compared to the native range, will enable better prediction of areas at risk of future invasions. Here, we characterise the ecological niche of the common myna ( Acridotheres tristis ) and common starling ( Sturnus vulgaris ), in their native range and in Aotearoa New Zealand, where they were introduced over 140 years ago. Common myna and common starling are two of the most invasive bird species in the world and are agricultural pests, competitors to native fauna and may act as disease vectors. Using biologically justified environmental variables and occurrence data, we construct ecological niche models (ENMs) using five algorithms. Based on the ENM algorithm with highest transferability, we identify key environmental variables to compare the niches of the two species in New Zealand and the native range, and between the two species in New Zealand. For both species, we find no evidence of niche divergence between New Zealand and their native range despite their long invasion history. However, we do find evidence for niche differences between the two species in New Zealand. Our future suitable habitat predictions suggest little range expansion of the already-widespread starlings in New Zealand, but large areas at risk of future myna invasion in New Zealand’s South Island. Our results support ongoing management of myna populations, especially in the South Island where the Cook strait may already provide some barrier to dispersal.

We surveyed the birds of East Kwaio, Malaita, Solomon Islands from 20 October to 2 November 2018. We conducted 66 point counts and recorded or observed 58 species of resident landbirds, including 23 of the 24 passerine species known from the island of Malaita and 15 waterbird species. We collected some form of samples (e.g., whole specimens and/or blood samples) from 61 individuals of 17 species, including representatives of the four species-level endemics: Malaita Fantail Rhipidura malaitae (Mayr, 1931), Malaita Dwarf-Kingfisher Ceyx malaitae (Mayr, 1935), Malaita White-eye Zosterops stresemanni (Mayr, 1931), and Red-bellied Myzomela Myzomela malaitae (Mayr, 1931). We demonstrate the considerable potential for conservation of the Malaitan avifauna on traditional lands in the mountains of East Kwaio. The extensive knowledge of the local people was a key factor in the success of the expedition. To facilitate ongoing conservation efforts, we documented the local Kwaio names of the birds we encountered.