Threats to Urban Bird Populations

Threats to urban Bird PopulationsEmily Bailes, Ann Bailey, Matheus Blezer Plumm, Tom McClellan-West, Lizzie Yarwood demonstrationThe enigmatic creatures of the sky, gentlewomans be creatures that argon treasu vehement by some around the world, by some as cultural symbolism, differents a hobby to indulge in and some just find their presence a pleasant addition to a grey and largely urban world.Human colonisation has had a coarse impact on nature, gentlewomans included, with some able to utilise the new urban habitat to undischarged way egress feral pigeons (Columba livia domestica) exploit waste products and buildings as a place to nest. However, some species require found it oft harder to adapt to the runty terrors that argon present within the ever increasing urban environs.In recent reports, the conservation status of 246 hissing species were evaluated of which 52 (21.1%) were placed on the Red list, 126 (51.2%) were on the Amber list and 68 species (27.6%) were p laced on the Green list (Eaton et al. 2009). Over a period of 35-45 years, there were 28 species with statistic bothy signifi provoket population declines of with child(p)er than 50%. One of these species is the Turtle Dove (Streptopelia turtur) according to the CBC/notice board trend it has showed a severe decline in abundance since the 1970s (Figure 1), and it is a priority species in the UK Bio diverseness Action Plan. In the period of 2002-2012 the Turtle Dove had an 80% decline in population coat in the UK.Whilst there are some threats facing urban shucks populations, there are quaternity pick out threats that feature been focused on in this review. Cat predation, windowpane collisions, habitat loss and usual human flap all fill variable effects on annulus abundance and have been discussed in the following paragraphs.Predation by FelinesWhilst there are several high risk threats to urban razzing populations, the most severe is that of cat predation. Cats have long been known to have a prejudicial ecological impact. They are responsible for multiple cases of extinctions in ground nesting birds in island habitats, where they come into contact with species possessing belittled or no defence mechanisms against predation. This inevitably leads to extinction. The current global impact of free-ranging domestic cats on bird deathrate is pictured to be up to 4 billion birds, annually ( disadvantage et al. 2013). In the UK alone it is estimated that crosswise a 4 month period, up to 100 million prey items are caught by cats, 24% of these cosmos bird species (Woods et al. 2003). With cats bringing home an average of 13.4 prey items per year (Heezik et al. 2010), this can have a forceful impact on wildlife populations. One study that focused on the bird populations of a typical urban UK village found that 16% of birds caught in a year were House Sparrows (Passer domesticus) which are a red listed and highly endangered species (British Trust for Orn ithology 2002) (Figure 2).It was also found in the same study that cats were responsible for 30% of Passer domesticus deaths in that area. Cats are also responsible for the deaths of many other red listed species such(prenominal) as the Starling (Sturnus vulgaris) (British Trust for Ornithology 2002) (See fig 3). Another more worrying issue is that the number of bird deaths emergenced if that mob was providing food for birds (Woods et al. 2003). This is especially troubling as cat owners trying to economize endangered species may be doing more harm than good. These trends all point to cat predation being the number one threat to urban bird populations.However, research has been conducted that advises that the impact of cats on ecosystems may not be wholly negative. As an apex predator, an animal with no natural predators of their own, cats have free reign to hunt in UK ecosystems without business of predation. As well as suppressing the abundance of birds they also frequently p redate other animals and some mesopredators such as rodents. Whilst their impact on bird diversity and population is clear, they also play a key ecological role in the suppression of birds natural predators (Ritchie Johnson 2009).Window CollisionsWindow collisions are considered to be the second largest cause of bird fatalities in urban areas (Loss et al. 2014). This however may not be accurate due to the lack of quantitative estimates and research on other continents (Bayne et al. 2012). There have been some attempts to estimate the number of fatalities per year within populations, however the US and Canada have had some input. Klem JR (1990a) estimated a put of 100 million to 1 billion birds killed per year within the USA, which was later considered to be a materialistic estimate (Klem 2006). Bayne et al. (2012) believed these estimates to be unlikely due to a lack of research in other geographic areas.Windows pose a threat as birds do not perceive glass within their vision, a nd they pass on tick off windows and corridors as a route to other habitat areas (Klem et al. 2009). Reflections from windows are also perceived as a continuation of the sky-both of these things occur during weak hours (Machtans et al. 2013). At night, windows become a source of light contaminant which is particularly a problem for migratory birds (Loss et al. 2014). Upon collision, birds suffer fatalities due to head traumas, intracranial pressures and bleeding on the brain, rather than the broken neck explanation (Klem 1990b), fortified by the terminuss found by Veltri Klem (2005) in which 91% of birds found dead from window collisions had no skeletal or cervical fractures.Urban environments, and the increase in buildings that feature glass, are proportionately linked to collision mortality judge (Hager et al. 2012). Glass is considered to be a non-selective lethal hazard by Klem (1990a) who found that sex, age and resident status does not affect the mortality rates of win dow collisions, neither is there a differentiation between smaller and larger species. However, this result may not be universal, with data but collected from two different buildings in differing locations. It would be favourable to take samples from a range of buildings in a number of locations around the world to see what impacts exist to which species, because although there is plausibly no difference between small and large species in basis of collision rate, those collisions impacts on individual species could be more profound.Whilst being a threat to individual birds in large quantities globally, in the US there is a lack of research into the effects of this particular mortality along with other collisions on population dynamics, with one study going as far to suggest that collisions with man-made structures, including windows has no discernible effect on the population trends in North America (Arnold coat 2011).Bayne et al. (2012) explain that more research needs to be do ne to obtain a reliable estimate for bird mortality caused by window collisions. Research can then be done to grasp a better perspective of what the mortalities are doing to the population numbers. This should also be done in other locations to give more clarity on the issue, and provide greater understanding moving forwards.Habitat LossHabitat loss is becoming a big issue over the world due to urbanisation from human development. On average in the united States, urbanised areas have as few as 35% shoetree coverage, with another 118,300km2 of forest land expected to be lost in the undermentioned 50 years. Forest land is important as not only does it provide shade, it also provides occult nesting areas and food (Lerman et al. 2014). Habitat fragmentation and habitat loss not only causes a community diversity loss within the animal kingdom, it removes the nesting areas for these birds, leaving them vulnerable. Bird feeders that can be found in peoples gardens can help to reduce t he lack of food caused by the removal of plants and trees, of which birds and their prey feed from. However this cannot prevent, or even counterbalance, the decrease in the diversity of species which are lost and replaced by non- innate species (Shochat et al. 2010). In Malaysia, nearly one-half of their land has been urbanised and changed by humans, causing a loss in biodiversity. However they have created little pockets within the urban areas for wildlife, such as nature reserves, topical anesthetic pose and plazas. Although, it has been noticed that exotic plant life is not popular with the native insects and their prey-which impacts majorly on the bird population. Despite exotic plants not helping to increase native bird numbers, they are still being planted for ornamental reasons and as part of their local plants scheme so this does not help with the conservation of native birds (Idilfitri Mohamad 2012).Human DisturbanceHuman disturbance is a threat to bird species in urban areas and can come in many forms ranging from contaminant of waterways to introduction of non-native species into the environment. Habitat fragmentation and introduction of exotic species to urban environments has seen a decline in urban bird populations. Within urban areas there are a range of habitats, from parks containing primarily native tree species, to recently certain streetscapes that do not contain any mature tree species. Here, many of the tree species found are non-indigenous. Other habitats that can be found in an urban environment are streetscapes with only native tree species, and those with only exotic tree species (White et al. 2005). Higher species richness of birds and abundance is observed in habitats with more resources, such as parks, with the greater availability of food and nesting sites. In habitats with non-indigenous tree species, nectarivorous birds are less prolific as flowers that they specialize in are not present. Insectivorous birds are also less gross in such habitats native insects have evolved with native plants, so impart be absent where these trees are absent, thus insectivorous bird species will be absent. Recently developed and exotic streetscapes often lack the shelter required for certain bird species, so these birds are operate out of potential habitats (Bhuller Majer 2000).Bird species require specific flora species within distinct habitats that meet all of their requirements some bird species are more tolerable of disturbed habitats with exotic species, whilst other species are parasitic on the native flora and undisturbed habitats. Urbanisation may lead to an increase in non-indigenous bird species and the simplification of bird communities if exotic plants are planted and streetscapes continue to be created. Therefore native plant life must continually be planted and parks protected in order to maintain mingled bird communities and conserve native bird species (White et al. 2005).The effects of light po llution from urban areas on birds are also of particular concern. A study conducted on European Blackbirds (Turdus merula) showed that birds exposed to 0.3 lux of illumination at night time had an irregular molt pattern with respect to individuals that were exposed to a dark night. mannish European blackbirds production of testosterone is stimulated annually by light, in a assist called photore divisoriness. After the breeding season, the birds stop being photosensitive, and so the gonads are diminished whilst they are not in use. Gonads re-develop after photostimulation by shorter daylight hours in the autumn and the increase in day length thereafter. chase long periods of exposure to light at night time, the reproductive cycles of male birds stop, with testosterone concentrations in the plasma at a minimum. Thus, it can be suggested that artificial light could confuse birds, as they miss important photo-cues for photorefactoriness. Without these cues, testosterone concentration s go on at a minimum, gonads fail to re-develop and the bird will not disgorge come breeding season. The light pollution caused by urban environments is a threat to urban bird populations, as it leaves individuals unable to reproduce through confusing their photosensitive reproductive cycles. (Dominoni et al. 2013)ConclusionIt is apparent that the threats mentioned in this review all have the potential to impact urban bird populations around the world and have all been reported in literature to have a negative effect on birds. However the threats mentioned have a great deal of complexity about them due to the interchangeable effects each threat can have on one another which may make distinguishing the effects of one individually difficult.A great example of this is the provision of bird feeders in gardens. Whilst the benefits of providing food will be greatly received by a number of bird species, it can increase the frequency of predation by cats (Woods et al. 2003). It is also sh own that providing bird feeders near urban buildings can increase the frequency of bird-window collisions (Klem 1990a). However, a dynamic could be present, where the fear factor of cats is influencing the birds into quick flight paths that lead them to collide with windows. It is here that the two dynamics of the threats are interlinked.Mortality rates of birds killed by window collisions with single building may be small, but deaths from window collisions with several buildings across the urban environment accumulate to give a high serving of mortality. To reduce this high percentage of mortality, something must be done to the structure of buildings (e.g. urban residences) so birds do not confuse window panes as a pathway, thinking that it is clear for them to use (Loss et al. 2014).Furthermore our constant introduction of exotic non-native species to parks and streetscapes changes the habitat and prey items available to urban birds which will further increase their population de cline- some bird species have easily adapted to changing conditions, whilst populations of others have been disturbed with the loss of specific habitats.Not only do the exotic species disrupt the local ecosystems, they also replace habitats that would otherwise be suitable for many native invertebrates that are an important source of food for birds. Whilst this threat isnt as obvious or as directly damaging to birds, it is still a serious threat to be considered and further researched. foreign plants are leading to declining native bird populations, but in spite of this they are still being planted for ornamental reasons (Idilfitri Mohamad 2012).Urbanisation may lead to an increase in non-indigenous bird species and the simplification of bird communities if exotic plants are planted and streetscapes continue to be created. Therefore native vegetation must continually be planted and parks protected in order to maintain complex bird communities and conserve native bird species (White et al. 2005).All things considered there are a number of aspects that need to be addressed. Bayne et al. (2012) pointed out how there is a lack of quantitative estimates and lack of research in other geographical areas as reasons why window collision mortality and its effects on a population may not have particularly accurate data. The statement could be extended to various aspects of urban bird population. Threats mentioned above would benefit from extra research, however this is difficult to achieve when the practicalities of working in an urban environment, resources and time are taken into consideration.ReferencesArnold, T.W., Zinc, R.M. (2011) Collision Mortality Has No Discernible Effect on Population Trends of North American Birds. PLoS ONE, 6, e24708Bayne, E.M., Scobie, C.A., Rawson-Clark, M. (2012) Factors influencing the annual risk of bird-window collisions at residential structures in Alberta, Canada. Wildlife Research, 39, 583-592.Bhuller, S., Majer, J.D. (2000) Arthr opods on street trees a food resource for wildlife. Pacific Conservation Biology, 6, 171-173.British Trust for Ornithology. (2002) Investigation into the causes of the decline of Starlings and House Sparrows in Great Britain. Norfolk BTODominoni, D.M., Quetting, M., Partecke, K. (2013) semipermanent Effects of Chronic Light Pollution on Seasonal Functions of European Blackbirds (Turdus merula). PLoS One, 8, e85069.Eaton, M.A., Brown, A.F., Noble, D.G., Musgrove, A.J., Hearn, R.D., Aebischer, N.J., Gibbons, D.W., Evans, A. Gregory, R.D. (2009) Birds of Conservation Concern 3 the population status of birds in the United Kingdom, Channel Islands and Isle of Man. British Birds, 102, 296341.Shochat, E., Lerman, S.B., Anderies, J.M., Warren, P.S., Faeth, S.H., Nilon, C.H. (2010) Invasion, Competition, and Biodiversity Loss in Urban Ecosystems. BioScience, 60, 199-208.Hager, S.B., Cosentino, B.J., McKay, K.J., Monson, C., Zuurdeeg, W., Blevins, B. (2012) Window Area and Development Drive Spatial Variation in Bird-Window Collisions in an Urban Landscape. PLoS ONE, 8, e53371.Heezik, Y.V., Smyth, A., Adams, A., Gordon, J. (2010) Do domestic cats impose an unsustainable harvest on urban bird populations? Biological Conservation, 143, 121-130.Klem JR, D. (1990a) Collisions between Birds and Windows Mortality and streak (Colisiones de Pjaros con Ventanas Mortalidad y Prevencin). ledger of Field Ornithology, 61, 120-128.Klem JR, D. (1990b) Bird Injuries, Cause of Death and Recuperation from Collisions with Windows. Journal of Field Ornithology, 61, 115-119.Klem JR, D. (2006) Glass A Deadly Conservation Issue for Birds. Bird Observer, 34, 73-81.Klem JR, D. Farmer, C.J., Delacretaz, N., Gelb, Y., Saenger, P.G. (2009) Architectural and Landscape seek Factors Associated with Bird-glass Collisions in an Urban Environment. The Wilson Journal of Ornithology, 121, 126-134.Lerman, S.B., Nislow, K.H., Nowak, D.J., DeStefano, S. King, D.J., Jones-Farrand, D.T. (2014) Using urban f orest assessment tools to model bird habitat potential. Landscape and Urban Planning, 122, 29-40.Loss, S.R., Will, T., Loss, S.S., Marra, P.P. (2014) Bird-building collisions in the United States Estimates of annual mortality and species vulnerability. The Condor, 116, 8-23.Loss, S.R., Will, T., Marra, P.P. (2013) The impact of free-ranging domestic cats on wildlife of the United States. Nature Communications, 4.Machtans, C.S., Wedeles, C.H.R., Bayne, E.M. (2013) A First Estimate for Canada of the Number of Birds Killed by Colliding with Building Windows. Avian Conservation and Ecology. 8, 6.PECBMS (2014)Trends of common birdsin Europe, 2014 update.CSO, Prague.Ritchie, E. G. Johnson, C. N. (2009) Predator interactions, mesopredator release and biodiversity conservation. Ecology Letters, 2, 982-998.Idilfitri, S., Mohamad, N.H.N. (2012) Role of Ornamental Vegetation for Birds Habitats in Urban Parks flake study FRIM, Malaysia. Procedia- Social and Behavioural Sciences, 68, 894-909.V eltri C.J. and Klem JR, D. (2005) Comparison of fatal bird injuries from collision with towers and windows. Journal of Field Ornithology, 76, 127-133.White, J.G., Antos, M.J., Fitzsimons, J.A., Palmer, G.C. (2005) Non-uniform bird assemblages in urban environments the influence of streetscape vegetation. Landscape and Urban Planning, 71, 123-135.Woods, M., McDonald, R. A., Harris, S. (2003) Predation of wildlife by domestic cat genus Felis catus in Great Britain. Mammal Review, 33, 174-188.