Feral pigeons as a nest competitor for a small seabird

Due to their life-history traits, the petrels are particularly sensitive to predation by introduced species. Therefore, many populations have constricted their original breeding distribution range, currently only occupying predator-free sites. In this scenario, interspecific competition for nesting sites can be detrimental for the petrel’ conservation. Here, we evaluate how the presence of introduced mammals (cats Felis catus and rats Rattus spp.) and potential competitors for nest sites (Cory’s shearwaters Calonectris borealis and feral rock pigeons Columba livia) shape the distribution, breeding density, and breeding performance of the Bulwer’s petrel Bulweria bulwerii on Tenerife, the largest and most densely populated of the Canary Islands. We estimated nest density, assessed the role of nest location and nest characteristics on breeding success, and determined causes of breeding failure by exotic predators and competitors. Nest density was higher in predator-free colonies on marine rocks. Cat presence was the best predictor for nest density, while presence or abundance of competitors had no correlation to nest density. Breeding success varied between years and colonies, but was not related to nest characteristics. Of the unequivocally determined causes of breeding failure, pigeon competition for nests was the most frequent (7.3%), followed by rat predation (6.3%). We also compared petrel and pigeon nest cavities and found a considerable overlap in nesting niche. Our study provides insight on an overlooked impact of the invasive rock pigeon: nest competition with small seabirds. We encourage more research on the effects of pigeons on nest density, disease and pathogen transmission, and vegetation changes within petrel colonies.

Seropositivity and Risk Factors of Brucella Infection in Small Ruminants that had History of Recent Abortion in the Afar Region of North-Eastern Ethiopia

Background: Brucellosis is one of the most important reproductive disease causes abortion and breeding failure in small ruminants and also causes severe systemic diseases in exposed humans. In Ethiopia, several studies of seroprevalence shows the magnitude and distribution of brucellosis both in animals and humans vary in different geographical localities. However, except few studies in Ethiopia all these serological studies was limited to RBPT and CFT, so far not supplemented with a varities of serological tests like ELISA to detect brucella infection, which is increase the likehood of detecting infected individulas and also improve the reliability of epidemiological data for appropriate control strategies. Hence, the present study was conducted in Amibara district of Afar Region, Ethiopia to detect the seropositivity and risk factor of Brucella infection in small ruminants that had history of recent abortion using mRBPT, cELISA and CFT. Materials and methods: Sera were collected from 226 animals (195 goats and 31sheep) and assessed for seropositivity of Brucella infection using modified Rose Bengal Plate Test (mRBPT), Complement Fixation Test (CFT) and competitive Enzyme Linked Immuno Sorbent Assay (cELISA).Results : In this study the over all seroprevalence was 12.0% (27 out of 226), 7.5% (17 out of 226) and 26.6% (60 out of 226) by mRBPT, CFT and cELISA, respectively. Out of 27 sera which were reactive by mRBPT, 17 (63.0%) were also reactive by (CFT). Out of the 17 sera which were reactive by CFT and mRBPT, 14 (82.4%) were reactive by cELISA. Out of the 29 sera which were non-reactive both by mRBPT and CFT, 10 (34.5%) were found to be reactive by cELISA. Out of the 226 sera which were tested both by mRBPT and cELISA, 20 (8.9%) were reactive by both tests, while 159 (70.4%) were non-reactive by both tests. The percentage of test agreement (79.2%) between mRBPT and cELISA was poor (k= 0.353). A high seropositivity for Brucella infection was significantly associated with the presence of retained placenta in the study animals (adjusted OR= 2.2, 95%CI, 1.1-4.4, P=0.030) as detected by cELISA. Conclusion: The findings of this study could suggest that brucellosis is main cause of abortion and breeding failure in small ruminants that had histry of recent abortion in the pastoral communities’ andwarrants the need for proactive measures to reduce its economic impact and risk of zoonotic transmission. This study indicates that cELISA based seroepidemiological survey increase the likehood of detecting infected individulas of brucellosis and also would be useful to provide reliable evidence for Brucella infection in small ruminants compared to mRBPT.

Seropositivity and risk factors of Brucella infection in small ruminants that had history of recent abortion in the afar region of north-eastern Ethiopia

Background: Brucellosis is one of the most important reproductive disease causes abortion and breeding failure in small ruminants and also causes severe systemic diseases in exposed humans. In Ethiopia, several studies of seroprevalence shows the magnitude and distribution of brucellosis both in animals and humans vary in different geographical localities. However, except few studies in Ethiopia all these serological studies was limited to RBPT and CFT, so far not supplemented with a varities of serological tests like ELISA to detect brucella infection, which is increase the likehood of detecting infected individulas and also improve the reliability of epidemiological data for appropriate control strategies. Hence, the present study was conducted in Amibara district of Afar Region, Ethiopia to detect the seropositivity and risk factor of Brucella infection in small ruminants that had history of recent abortion using mRBPT, cELISA and CFT. Materials and methods: Sera were collected from 226 animals (195 goats and 31sheep) and assessed for seropositivity of Brucella infection using modified Rose Bengal Plate Test (mRBPT), Complement Fixation Test (CFT) and competitive Enzyme Linked Immuno Sorbent Assay (cELISA).Results : In this study the over all seroprevalence was 12.0% (27 out of 226), 7.5% (17 out of 226) and 26.6% (60 out of 226) by mRBPT, CFT and cELISA, respectively. Out of 27 sera which were reactive by mRBPT, 17 (63.0%) were also reactive by (CFT). Out of the 17 sera which were reactive by CFT and mRBPT, 14 (82.4%) were reactive by cELISA. Out of the 29 sera which were non-reactive both by mRBPT and CFT, 10 (34.5%) were found to be reactive by cELISA. Out of the 226 sera which were tested both by mRBPT and cELISA, 20 (8.9%) were reactive by both tests, while 159 (70.4%) were non-reactive by both tests. The percentage of test agreement (79.2%) between mRBPT and cELISA was poor (k= 0.353). A high seropositivity for Brucella infection was significantly associated with the presence of retained placenta in the study animals (adjusted OR= 2.2, 95%CI, 1.1-4.4, P=0.030) as detected by cELISA. Conclusion: The findings of this study could suggest that brucellosis is main cause of abortion and breeding failure in small ruminants that had histry of recent abortion in the pastoral communities’ andwarrants the need for proactive measures to reduce its economic impact and risk of zoonotic transmission. This study indicates that cELISA based seroepidemiological survey increase the likehood of detecting infected individulas of brucellosis and also would be useful to provide reliable evidence for Brucella infection in small ruminants compared to mRBPT.

Factors affecting nestling condition and timing of egg-laying in the endangered Carnaby’s cockatoo, Calyptorhynchus latirostris

Carnaby’s cockatoo, Calyptorhynchus latirostris, is endemic to south-western Australia. It has undergone a major decline in range and abundance as a result of extensive removal of breeding and foraging habitat. It is now classified as endangered by the State of Western Australia, the Australian government, and internationally. In order to plan effective conservation management for the species it is important to assess the success of breeding populations throughout its range. In this paper we examine the efficacy of using the relationship between growth in the length of a nestling’s folded left wing and body mass to assess nestling condition, and examine known breeding failure in relation to nestling condition in two breeding populations: one at Coomallo Creek (studied from 1970–2017), and the other at Manmanning (1969–76). Results demonstrated that the lighter the nestlings, the higher the rate of breeding failure. Data from the Coomallo Creek population were used to prepare a table of nestling folded left wing length and body mass as a benchmark for assessing nestling condition in 10 other breeding populations, based on data collected from 1970 to the present. Following extensive clearing that removed foraging and breeding habitat, two of the 10 populations produced nestlings that were significantly lighter than the benchmark, and both populations subsequently declined to extinction. The commencement of egg-laying each season at Coomallo Creek was strongly influenced by total rainfall in the first half of autumn. The length of the egg-laying period between 1970–76 and 2009–17 increased by 5.2 weeks (40%). This increase was related to changes in rainfall and temperature over more than four decades. Despite the lengthening of the egg-laying period, nestling condition was unaffected, suggesting that, at least in the short term, the Carnaby’s cockatoo population at Coomallo Creek is coping with the effects of climate change.

Chronic, sublethal effects of high temperatures will cause severe declines in southern African arid-zone birds during the 21st century

Birds inhabiting hot, arid regions are among the terrestrial organisms most vulnerable to climate change. The potential for increasingly frequent and intense heat waves to cause lethal dehydration and hyperthermia is well documented, but the consequences of sublethal fitness costs associated with chronic exposure to sustained hot weather remain unclear. Using data for species occurring in southern Africa’s Kalahari Desert, we mapped exposure to acute lethal risks and chronic sublethal fitness costs under past, present, and future climates. For inactive birds in shaded microsites, the risks of lethal dehydration and hyperthermia will remain low during the 21st century. In contrast, exposure to conditions associated with chronic, sublethal costs related to progressive body mass loss, reduced nestling growth rates, or increased breeding failure will expand dramatically. For example, by the 2080s the region will experience 10–20 consecutive days per year on which Southern Pied Babblers (Turdoides bicolor) will lose ∼4% of body mass per day, conditions under which this species’ persistence will be extremely unlikely. Similarly, exposure to air temperature maxima associated with delayed fledging, reduced fledgling size, and breeding failure will increase several-fold in Southern Yellow-billed Hornbills (Tockus leucomelas) and Southern Fiscals (Lanius collaris). Our analysis reveals that sublethal costs of chronic heat exposure are likely to drive large declines in avian diversity in the southern African arid zone by the end of the century.

Emperors on thin ice: three years of breeding failure at Halley Bay

Satellite imagery is used to show that the world's second largest emperor penguin colony, at Halley Bay, has suffered three years of almost total breeding failure. Although, like all emperor colonies, there has been large inter-annual variability in the breeding success at this site, the prolonged period of failure is unprecedented in the historical record. The observed events followed the early breakup of the fast ice in the ice creeks that the birds habitually used for breeding. The initial breakup was associated with a particularly stormy period in September 2015, which corresponded with the strongest El Niño in over 60 years, strong winds, and a record low sea-ice year locally. Conditions have not recovered in the two years since. Meanwhile, during the same three-year period, the nearby Dawson-Lambton colony, 55 km to the south, has seen a more than tenfold increase in penguin numbers. The authors associate this with immigration from the birds previously breeding at Halley Bay. Studying this ‘tale of two cities’ provides valuable information relevant to modelling penguin movement under future climate change scenarios.

Nestling begging calls increase predation risk by corvids

Despite nest predation being the most common cause of breeding failure in open-nesting birds, we have little insight into the cues used by nest predators when they search for nests. So far we have assumed that nest-predating birds are visually oriented while mammal predators to a large extent use scent and auditory cues like nestling begging calls. To evaluate how important nestling begging calls are for corvid nest predators searching for nests, I used artificial nests, which made it possible to find the real costs of the begging without mitigation by parental and nestling behavior. I used paired artificial nests, one with and one without nestling begging call playback. Within 10 days, 62.9% of the nests were predated. The analyses showed that nests with begging calls suffered a significantly higher predation rate than nests without begging calls, especially when the nests were placed close to corvid nests. Moreover, nests with begging calls were predated significantly earlier than nests without begging calls. In artificial nest pairs with both nests predated but on different days, nests with begging calls were predated first. In nest pairs with only one predated nest, nests with begging calls were predated most often. This experiment shows that nestling begging calls imply a cost in terms of increased and earlier nest predation, and that corvids use nestling begging calls as a cue to find and depredate bird nests, challenging earlier expectations.

Raptors are still affected by environmental pollutants: Greenlandic Peregrines will not have normal eggshell thickness until 2034

The DDT-induced effects, eggshell thinning and breeding failure in Peregrine Falcon (Falco peregrinus) populations were reverted with restrictions on the use of the compound from the 1970s, and in most studied populations, the eggshell thickness is back to normal. In Greenland, a previous study of eggshell thinning in Peregrines found that shells had not yet reached pre-DDT levels. In this study, we extend the time series and reinterpret shell thinning data for 196 clutches covering a 45-year time span (1972–2017). There was a significant (P<0.001) increase in the eggshell thickness of 0.23% per year. This corresponds to a change in eggshell thinning from 14.5% to 5.4% in 2017 compared to the pre-DDT mean. With the current rate of change, pre-DDT shell thickness is predicted to be reached around the year 2034. However, a few clutches are still below the critical limit. The relatively slower recovery of the shell thickness in the Greenland population is likely indicative of the slower phasing out of DDT in the Greenlandic Peregrines’ wintering grounds in Latin America. The shell thinning in the Greenlandic population probably never crossed the 17% threshold associated with population declines, contrary to the populations in many other parts of the world.