Exposure to predators reduce immune response in birds

Navarro, C., De Lope, F., Marzal, A., & Møller, A. P. (2004). Predation risk, host immune response, and parasitism. Behavioral Ecology, 15(4), 629-635.

Predation risk may affect the allocation priorities of limiting resources by potential prey. Investment in immune function should receive reduced priority, when hosts are exposed to predators because of the costs of immune function. We tested this hypothesis by randomly exposing adult house sparrows, Passer domesticus, to either a cat, Felis catus, or a rabbit, Oryctolagus cuniculus, for 6 h while assessing their ability to raise a T-cell–mediated immune response to a challenge with phytohemagglutinin. Sparrows exposed to a cat had a significant reduction of, on average, 18% and 36% in T-cell response in two different experiments compared with sparrows that were exposed to a rabbit. In a field experiment with a barn owl, Tyto alba, or a rock dove, Columba livia, placed next to a nest-box during laying, we found a mean reduction in T-cell–mediated immune response of 20%. In males, the reduction in cell-mediated immune response owing to cat exposure increased with increasing size of the badge, which is a secondary sexual character, but only during the breeding season. In a third experiment, house sparrows were either exposed to a barn own, T. alba, or a rock dove, C. livia, and development of malarial infections was recorded during the following 6 weeks. Individual sparrows exposed to a predator had a higher prevalence and intensity of Haemoproteus malarial infection than did control individuals. Therefore, exposure to predators reduced their ability of hosts to cope with parasitism mediated through effects on immune function.

Domestic dogs as nest predators of Wilson’s plover in northeastern Brazil

Diniz, C. G., de Morais Magalhães, N. G., Guerreiro, D., Diniz, P. D. C. P., Paulo, D. C., Renato, F., ... & Diniz, C. W. P. (2016). Cães domésticos predadores de ninho de batuíra bicuda (Charadrius wilsonia) no nordeste brasileiro. Revista da Biologia, 16(1), 24-27. 

Although Wilson´s plovers (Charadrius wilsonia) are migratory, a resident population breeds in coastal northeastern Brazil and there population trend is described as decreasing by the IUCN Red List. Domestic dogs are a major predator of Wilson’s plover nests on an island in northeastern Brazil where dogs are kept to guard fishing equipment. Local fishermen, however, are motivated to protect the nests of shorebirds and when shown video recordings documenting nest predation acted quickly to remove dogs. We found that providing local residents with evidence about the causes of nest
predation could play an effective role in protecting bird populations.

Cat predation on wildlife in Haute Savoie, France

Vuagnat-Kolter, M. Prédation du chat domestique, Felis catus (linnaeus, 1758) sur la faune sauvage, dans une commune péri-urbaine de Haute-Savoie (74). Le Bièvre, 22.

Le chat domestique, Felis catus (Linnaeus, 1758) est une espèce invasive, un redoutable prédateur et un animal de compagnie qui ne dépend pas de la disponibilité des proies pour survivre. Ces trois aspects associés à l’importante densité de chats font de sa prédation sur la faune sauvage, un facteur important dans le fonctionnement des écosystèmes, qui peut entraîner localement le déclin d’espèces
indigènes. La présente étude a eu lieu en Haute-Savoie dans la commune de Feigères. Toutes les proies  ramenées au domicile par 44 chats domestiques ont été identifiées sur une durée de 3 mois. Un total de 163 proies ont été tuées (86 micromammifères, 69 oiseaux, 8 reptiles) pour une moyenne de 3,7 proies par chat. Neuf espèces d’oiseaux ont été identifiées, parmi lesquelles le moineau domestique (58 %) est le plus représentée devant le merle noir (13  %). Le moineau domestique est placé en première position car il est commensal de l’homme et vit dans toutes sortes de zones modifiées par celui-ci, notamment les jardins. L’extrapolation des résultats à l’échelle de la commune montre que 2068 proies dont 878 oiseaux ont été potentiellement tuées sur trois mois entre mi-avril et mi-juillet. Le suivi télémétrique réalisé sur une durée de cinq semaines sur cinq chats, a permis de démontrer que les chats sont inactifs la majeur partie du temps (77 %) et que leurs périodes d’activité privilégiées sont l’aube et le crépuscule, lorsque les températures sont les plus basses de la journée. Le domaine vital des chats est relativement petit, ils n’effectuent pas de grandes distances et occupent principalement leur foyer ainsi que le jardin attenant à celui-ci.

The domestic cat Felix catus (Linn. 1758) is an invasive species, a formidable predator and a pet which is not dependent on the availability of prey for its survival. These three elements, plus the high density of cats, make its preying on wildlife a major factor in the functioning of ecosystems. This can lead to a decline in indigenous species locally. The present study took place in the Haute-Savoie department (France), in the commune of Feigères. All the prey brought home by 44 domestic cats were identified over a period of 3 months. There were 163 prey items in all (86 small mammals, 69 birds and 8 reptiles) for an average of 3.7 prey items per cat. 9 species of bird were identified, among which the House Sparow was the most numerous (58  %) followed by Blackbird (13  %). The House Sparrow came first because it is closely associated with man and lives in all sorts of places modified by him, notably gardens. Extrapolating the results to the scale of the commune produces 2068 prey items including 878 birds which were potentially killed over the three-month period from mid-April to mid-July. Radiotracking carried out on 5 cats over 5 weeks showed that cats are inactive most
(77  %) of the time. Their preferred periods of activity are dawn and dusk when the day temperatures are at their lowest. The cats’ territories are relatively small, not covering large distances, and mainly
occupy their homes and the adjacent gardens.

Domestic dogs as nest predators of shorebirds in NE Brazil

Diniz, C. G., de Morais Magalhães, N. G., Diniz, D. G., Pereira, P. D. C., Paulo, D. C., Renato, F., Sherry, D.F. & do Pará, T. Domestic Dogs as Nest Predators of Wilson’s plover (Charadrius wilsonia) in Northeastern Brazil.

Although Wilson´s plovers (Charadrius wilsonia) are migratory, a resident population breeds in coastal northeastern Brazil and there population trend is described as decreasing by the IUCN Red List. Domestic dogs are a major predator of Wilson’s plover nests on an island in northeastern Brazil where dogs are kept to guard fishing equipment. Local fishermen, however, are motivated to protect the nests of shorebirds and when shown video recordings documenting nest predation acted quickly to remove dogs. We found that providing local residents with evidence about the causes of nest predation could play an effective role in protecting bird populations. 

Alien predator control to benefit endangered Hawaiian waterfowl

Underwood, J. G., Silbernagle, M., Nishimoto, M., & Uyehara, K. J. 2014. Non-native Mammalian Predator Control to Benefit Endangered Hawaiian Waterbirds. Proc. 26th Vertebr. Pest Conf. (R. M. Timm and J. M. O’Brien, Eds.) Published at Univ. of Calif., Davis. 2014. Pp. 32-39.

Hawai‘i’s wetlands are inhabited by 5 endangered endemic waterbird species: the Hawaiian stilt (ae‘o), Hawaiian coot (‘alae ke‘oke‘o), Hawaiian duck (koloa maoli), Hawaiian goose (nēnē), and Hawaiian gallinule/Moorhen (‘alae ‘ula). One of the biggest threats facing these waterbirds is predation by non-native mammalian predators. Non-native cats, rats, and mongooses all directly depredate either eggs, young, or adult birds. Control of these predators is a key component of the active management strategy employed to recover Hawaiian waterbirds. Predator control efforts have included live or kill traps, rodenticide bait stations, and fences in areas important for the waterbirds. To evaluate the success of these predator control efforts on key wetland national wildlife refuges in Hawai‘i, we explored 4 metrics: live trap capture history, rodent and mongoose presence/absence using track tunnels, waterbird population densities, and waterbird reproductive success. The track tunnel data documented lower predator density within the predator control areas. The live trapping capture history data showed strong spatial patterns of higher success along perimeter fence lines and limited success within the interior of the wetlands. We also found that areas receiving predator control had both higher reproductive success and, in most cases, greater waterbird population densities. These findings support mammalian predator control as a key management strategy to promote recovery of these endangered species.

Habitat and mesopredator activity as predictors of bird densitiy in urban parks

Thieme, J. L., Rodewald, A. D., Brown, J., Anchor, C., & Gehrt, S. D. (2015). Linking Grassland and Early Successional Bird Territory Density to Predator Activity in Urban Parks. Natural Areas Journal, 35(4), 515-532.

The proximity of urban green spaces to anthropogenic food sources can promote high densities of predators that may negatively affect breeding birds. Not only can high numbers of predators depress reproduction and survival, but birds may behaviorally respond by avoiding those patches, thereby diminishing the value of urban habitats. During 2010 and 2011, we examined relationships between avian territory density and activity of nest predators in 36 2-ha plots within six urban grassland and early successional parks (sites) near Chicago, Illinois. At the plot (i.e., local) scale, densities of common yellowthroats (Geothlypis trichas), field sparrows (Spizella pusilla), and savannah sparrows (Passerculus sandwichensis) were more strongly linked to habitat characteristics than predators. Song sparrow (Melospiza melodia) and eastern meadowlark (Sturnella magna) densities were not associated with habitat at the plot scale, but together were negatively related to activity of avian predators. Surprisingly, densities of song sparrows were positively associated with snake activity at both plot and site (i.e., landscape) scales, and densities of savannah sparrows increased moderately with activity of mesopredators at the site scale. Our results suggest that although habitat structure is a strong predictor of grassland bird densities in this urban matrix, activity of predators also may contribute to patterns of territory selection of certain bird species. With this in mind, managers encouraging settlement of grassland birds within urban preserves may consider (a) increasing dense groundcover that provides protective cover for songbirds, and (b) discouraging activities that promote activity of avian predators, particularly corvids.

Cat vectored toxoplasmosis among the main causes of mortality in endangered Nene

Work, T. M., Dagenais, J., Rameyer, R., & Breeden, R. (2015). Mortality patterns in endangered Hawaiian geese (Nene, Branta sandvicensis). Journal of Wildlife Diseases, 51(3), 688-695.

Understanding causes of death can aid management and recovery of endangered bird populations. Toward those ends, we systematically examined 300 carcasses of endangered Hawaiian Geese (Nene; Branta sandvicensis) from Hawaii, Maui, Molokai, and Kauai between 1992 and 2013. The most common cause of death was emaciation, followed by trauma (vehicular strikes and predation), and infectious/inflammatory diseases of which toxoplasmosis (infection with Toxoplasma gondii) predominated. Toxicoses were less common and were dominated by lead poisoning or botulism. For captive birds, inflammatory conditions predominated, whereas emaciation, trauma, and inflammation were common in free-ranging birds. Mortality patterns were similar for males and females. Trauma predominated for adults, whereas emaciation was more common for goslings. Causes of death varied among islands, with trauma dominating on Molokai, emaciation and inflammation on Kauai, emaciation on Hawaii, and inflammation and trauma on Maui. Understanding habitat or genetic-related factors that predispose Nene (particularly goslings) to emaciation might reduce the impact of this finding. In addition, trauma and infection with T. gondii are human-related problems that may be attenuated if effectively managed (e.g., road signs, enforcement of speed limits, feral cat [Felis catus] control). Such management actions might serve to enhance recovery of this endangered species.

Vulture-canid competition

Campbell, M. (2015). Biodiversity and Vulture-Canid Relations. J Biodivers Endanger Species, 3, e122.

Conclusions
The evidence hints that the more eagle-like Old World vultures have a more equal relationship than the New World vultures with scavenging canids. Further study on this difference is important for three reasons. Vultures have declined in many Eurasian and African countries and canids (including feral dogs) have increased their scavenging role. Hence, a vulture population recovery must acknowledge the competitive role of canids. Also, as condor recovery programs are gathering ground in the Americas, the coyotes are possible impediments, possibly to a greater degree than jackals would be to old world vultures. Canids have a strong sense of smell and may precede vultures at hidden carcasses (condors and Old World vultures lack a sense of smell), hence when more visible carcasses are removed for sanitation purposes, conflicts may emerge between vultures and canids over the few remaining food sources. This encourages possibilities for detailed field research, which may increase our knowledge of the ecological relations of vultures and link the somewhat disparate studies of vulture evolution and biology with ecology and conservation possibilities.

Cats killing endangered night parrot

The latest twist in the rather secret story of the Night Parrot (Pezoporus occidentalis) is that a cat-killed individual has been found in an area of arid spinifex country SW of Winton, in W Queensland, close to where John Young photographed the species for the first time in May 2013.
Apparently, according to Queensland government sources, professional marksmen have been employed by a private conservation company to patrol the area at night with spotlights, shooting feral cats (Felis catus) on sight. The programme is funded by mining company Fortescue Metals, whose involvement dates back to the reported discovery of Night Parrots in a mineral exploration area in Western Australia in 2005. However, government agencies have been kept in the dark concerning the whereabouts of Night Parrots in Queensland, and the sites where the species occur are on a privately leased grazing property. Feral cats have long been implicated in the decline of this once widespread species: in 1892, it was reported that ‘numerous’ parrots were killed by cats near Alice Springs. Some observers have noted increases in feral cat populations in recent years in parts of inland Australia. The region around Winton where the parrots occur has been drought-afflicted for several years.

Are birds winners or loosers in cities?

Shochat, E. 2004. Credit or debit? Resource input changes population dynamics of city-slicker birds. Oikos 106:622-626.

The underlying evolutionary mechanisms of urban bird populations have hardly been studied. High food density and low predation risk serve to explain the global pattern of extremely high urban bird population densities. Both these bottom-up and top-down effects are paradoxical since the per capita amount of food is small due to competition, and domestic predator density is high in cities. The bottom-up paradox can be resolved by taking into account the high food resource-predictability in cities. Concerning the top-down effect, recent studies suggest that at least when it comes to nest predation the effect of cats is minor. I suggest that the combination of high food predictability and low predation risk in cities alter bird foraging behaviour, which in turn affects population dynamics. In terms of density, the result is that bird populations exceed the carrying capacity of the urban environment, costing heavily on body condition and/or life span. Under such conditions the population should consist of a few winners and many losers. Only the winners have sufficient access to food resources and the opportunity to reproduce. The highly predictable continuous input of food in the urban environment allows them to “live on their credit”. They may trade off between offspring body condition and clutch size. In the lack of predation, the losers among the fledglings may survive for a relatively long period, getting just enough energy to survive. Though they may never become healthy enough to reproduce, they will have a major contribution to the observed population density. Results of several case studies seem to support the credit card hypothesis and suggest that it can serve as a general rule for the evolution of animal populations and communities in highly predictable human managed environments.

Cat catched on camera at a Black Parrot nest site

from www.sif.sc/ 

A cat captured on camera at a Black Parrot nest site © SIF

Predation by invasive alien species has again proven to be a major problem for the black parrot during this breeding season. Through camera traps set up at a nest in Fond Peper, the team have observed cats climbing trunks and removing chicks from a nest. Eggs have also disappeared or been found broken in the nest which is probably due to rat predation. The team will keep monitoring the nests and the birds until the end of the season in March, and we look forward to reporting our first Black Parrot fledgling!

Cat eating endangered honeycreeper

The non-native feral cat in Hawaii is the most threatening predator to critically endangered palila. Palila did not evolve with these predators and are especially vulnerable to them. Evidence of their vulnerability was documented by researchers studying nest success of palila using continuous-loop video cameras to monitor the nests. Based on predation rates of the nests monitored, feral cats cause about 10% of all palila nests to fail every year.

Cute, isn't it?

Feral cat hunting in backyard

Feral Cat Documentary. A beautiful feral cat starts hunting backyard wildlife - a dilemma for animal lovers! I decide to watch, film and try to get to know this wild creature and see if a win-win solution is possible.

Urbanisation, predation and house sparrow populations

De Coster, G., De Laet, J., Vangestel, C., Adriaensen, F., & Lens, L. (2015). Citizen science in action—Evidence for long-term, region-wide House Sparrow declines in Flanders, Belgium. Landscape and Urban Planning, 134, 139-146.

Urban expansion is detrimental for many species. While the House Sparrow (Passer domesticus) initially flourished in the vicinity of men, a decline in House Sparrow numbers has been observed in several European cities during the last decades. A lack of systematic data on the status of this species in the highly urbanized Flanders (Belgium) has been the reason why since 2002, the Flemish population has been called annually to count House Sparrows during the breeding season. Here, we describe the results of the first ten years of sparrow counting. While inhabitants from 99% of the municipalities participated at least once, large differences in numbers of participants were observed among municipalities: the larger the population size, the more people counted sparrows. Results indicated that House Sparrow abundances have been decreasing in Flanders over the past decade. Contrary to several other European regions, the decline appears equally strong in rural and urban areas. However, average numbers of House Sparrows were lower in more densely populated, urban areas, and where less cropland, grassland and parks surrounded the sampling location. House Sparrow abundances also decreased significantly over time at locations where predator pressure increased. These results suggest that the House Sparrow decline in Flanders is due to the ever encroaching urbanization and the reduction of the amount of green space. Furthermore, it shows that data collection by volunteers can be a useful approach to obtain large-scale and long-term data in a relatively easy way, in addition to raising public awareness to the natural environme

Resolving the urban nest predator paradox: the role of alternative foods for nest predators

Stracey, C. M. (2011). Resolving the urban nest predator paradox: the role of alternative foods for nest predators. Biological Conservation, 144(5), 1545-1552.

Urbanization is a leading cause of species endangerment in the United States; however, certain species thrive in urban habitats. The loss of key predators or the addition of new predators in urban areas could alter the structure of urban communities. A reduction in nest predation is hypothesized to explain the high density of urban birds, yet urban areas typically have increased populations of avian nest predators. The loss of important nest predators in urban habitats, prey switching of urban predators, or successful nest defense against avian nest predators could explain this urban nest predator paradox. To assess these hypotheses I compared nest predation rates of Northern mockingbirds (Mimus polyglottos) in parking lots and residential neighborhoods to populations in pastures and wildlife preserves during 2007–2009 in Florida, USA and placed video cameras on a subset of nests in 2008–2009. Data do not support the hypothesis that urban nest predation rates are consistently lower than non-urban nest predation rates. Of the 56 nest predation events recorded, cats were the dominant urban predator and Cooper’s hawks (Accipiter cooperii) were the dominant non-urban predator. There was no evidence for a loss of important nest predators in urban habitats; however, prey switching by Cooper’s hawks likely occurred. There was also indirect evidence for the importance of nest defense. Furthermore, some of the cats recorded as nest predators in residential neighborhoods were owned cats and all but one cat predation event occurred at night. To reduce nest predation rates, cat owners should keep their cats indoors at night.

Cats seem to predate on birds with lower immunocompetence

Møller, A.P. & Erritzøe, J. 2000. Predation against birds with low immunocompetence. Oecologia. 122(4): 500–504.

Differences in the phenotypic characteristics between individuals falling prey to predators and conspecifics avoiding predation will reflect the intensity of selection on prey. If prey are generally in poor condition, we predicted that they should have an inferior health status in comparison to individuals dying for other reasons. We investigated this prediction for prey and conspecifics that did not die from predation by comparing the size of the spleen, which is an important immune defence organ reflecting one component of immunocompetence, using 18 species of passerine birds and domestic cat Felis catus predators as a model system. Prey had consistently smaller spleens than non-prey, implying that they had weak immune systems. The data set did not indicate that sex or age, month of death, body mass, body condition, liver mass, wing length or tarsus length differed significantly between prey and non-prey. Thus there was little evidence of confounding factors affecting the results. These observations indirectly suggest that disease and parasitism may play an important role in predator-prey interactions.

Mean (+SE) spleen mass (g) for birds captured by cats (Prey) and other conspecifics (Others). Numbers are sample sizes

Fatal toxoplasmosis in endemic NZ birds

Howe, L., Hunter, S., Burrows, E., & Roe, W. (2013). Four cases of fatal toxoplasmosis in three species of endemic New Zealand birds. Avian Diseases.  58(1): 171-175

Four cases of fatal toxoplasmosis in three endemic avian species are reported. Between 2009 and 2012, two kereru, one North Island brown kiwi, and one North Island kaka were submitted for necropsy examination. On gross post mortem the kiwi had marked hepatosplenomegaly while the kaka and two kereru had swollen, slightly firm deep red lungs. Histologically, there was extensive hepatocellular necrosis in the liver of the kiwi while the kaka and kereru showed severe fibrinous bronchointerstitial pneumonia. In the kiwi, protozoal organisms were present within both hepatocytes and Kupffer cells of the liver and within the epithelial cells and macrophages of the interstitium of the lung in the kaka and two kereru. The diagnosis of toxoplasmosis was confirmed with immunohistochemistry and PCR on the liver and/or lung of paraffin embedded formalin-fixed tissue. Genotyping of up to seven markers revealed an atypical Type II isolate of T. gondii was present in at least three of the cases. This study provides evidence that T. gondii can cause mortality in these endemic species and suggests further research is needed to determine that full extent of morbidity and mortality caused by this parasite in New Zealand's unique avifauna.

People and dogs disturbing birds on the beach

Lafferty, K. D. (2001). Birds at a Southern California beach: seasonality, habitat use and disturbance by human activity. Biodiversity & Conservation, 10(11), 1949-1962.

Use of a Santa Barbara beach by people and birds varied in both time and space. There were 100 birds, 18 people and 2 dogs per kilometer. Bird density varied primarily with the season and tide while human activity varied most between weekend and weekday. Bird distributions along the beach were determined mainly by habitat type (particularly a lagoon and exposed rocky intertidal areas) For crows and western gulls, there was some evidence that access to urban refuse increased abundance. Interactions between birds and people often caused birds to move or fly away, particularly when people were within 20 m. During a short observation period, 10% of humans and 39% of dogs disturbed birds. More than 70% of birds flew when disturbed. Bird species varied in the frequency that they were disturbed, partially because a few bird species foraged on the upper beach where contact with people was less frequent. Most disturbances occurred low on the beach. Although disturbances caused birds to move away from humans, most displacement was short enough that variation in human activity did not alter large-scale patterns of beach use by the birds. Birds were less reactive to humans (but not dogs) when beach activity was low.

Human and dog disturbance to shorebirds

McCrary, M. D., & Pierson, M. O. (2000). Influence of human activity on shorebird beach use in Ventura County, California. In Proceedings of the fifth California Islands symposium (pp. 424-427).

We studied the potential influence of human and dog activity on shorebird abundance at 13 sandy beaches in Ventura County, California. The 13 study beaches were randomly selected, and each beach was 1 km long. From June 1994 to May 1997, we counted all shorebirds, humans and dogs at each beach once per month for a total of 36 counts. We found no significant relationship between instantaneous counts of either shorebirds and human or dogs. However, there was a significant relationship among the 13 beaches between total shorebird and human use. The beaches with the greatest number of shorebirds (Ormond Beaches 1 through 3) were among those with the lowest number of humans. The results suggest that inaccessibility to humans may be an important aspect of shorebird habitat quality. Relatively undisturbed sandy beaches are quite rare in southern California, and the inaccessibility of the few remaining undisturbed beaches should be maintained.