Potential impact of grey squirrels Sciurus carolinensis on woodland bird populations in England

Several woodland bird species have declined markedly in abundance in England over the past 40 years, whilst the grey squirrel Sciurus carolinensis, a non-native nest predator, has increased. Given the timing, there has been concern that grey squirrels have driven these declines, although there is little data to support this view. Using novel analytical methods and extensive national bird and grey squirrel monitoring data, we examine whether there is evidence that woodland bird populations in England have been depressed by grey squirrels and whether there is a relationship between nest failure and squirrel numbers. Our results indicate that grey squirrels are very unlikely to have driven observed declines of woodland birds in recent years, although the number of associations, positive as well as negative, between grey squirrels and woodland birds is greater than expected by chance. For this reason, we cannot exclude the possibility that the populations of a small number of bird species, principally increasing species, have been depressed to some degree at sites where a greater number of grey squirrels were present. Of these species, perhaps the most convincing evidence is for Common Blackbird Turdus merula and Eurasian Collared Dove Streptopelia decaocto where nest record data also identified a positive relationship between nest failure at the egg stage and squirrel abundance.     

THE SOCIABLE WEAVER,PART 2: NEST ARCHITECTURE AND SOCIAL ORGANIZATION

Maclean, G. L. 1973. The Sociable Weaver, Part 2: Nest architecture and social organization. Ostrich 44:191-218.

Sociable Weavers build nest masses in a number of indigenous tree species (especially on Acacia giraffae branches) and on artificial nest sites like telephone poles. They never build in exotic trees. Nest masses are built of grass straws and roofed over with a superstructure of coarser material such as thorn twigs. The grass substructure contains the nest chambers which do not interconnect. The substructure may be divisible into two or more levels, each forming a social unit comprising the birds inhabiting it.

Each social level of birds is confined to its own structural level at all times, but a bird may roost in any chamber within its own level. The superstructure is not divisible into social units and any bird may build or perch on any part of the superstructure. Movements of birds from one colony to another are rare. The colony at one nest mass leaves the nest at about sunrise in summer, a little later in winter, and flies to the feeding grounds; the birds return to the nest mass for a siesta lasting from about 10:00 hours to 14:00 hours in hot weather, less than this in cool weather. They depart again for their feeding grounds until about sunset.

The internal temperature and RH of the nest chambers were not found to be significantly different from ambient temperature and RH when ambient temperatures were > 21,7°C. At ambient temperatures < 26,7°C the RH of the nest chambers was significantly lower than ambient Rh, but temperatures were not significantly different during the day.     

Colony success of the submissive ant Formica fusca within territories of the dominant Formica polyctena

Abstract. 1. Twenty-three nests of the submissive ant Formica fusca L. were sampled in two adjacent territories of the dominant wood ant Formica polyctena Först. The nests were dug up at different distances from the wood-ant mounds. Distance is assumed to be inversely related to the extent of disturbance of F. fusca by F. polyctena.
2. Colony success of F. fusca was assayed by counting the numbers of workers (colony size), and worker and sexual offspring in a nest. For individual size, the head width and dry weight of fifty workers per nest were measured.
3. Colony size correlated positively with the numbers of worker and sexual offspring in one territory, but only with worker offspring in the other.
4. Distance from the wood-ant mound correlated positively with colony size and numbers of worker and female offspring in one territory. In the other territory distance correlated positively with number of females, but negatively with number of worker offspring. No significant correlations between distance and the size measurements were obtained.
5. Because of its nonaggressive behaviour F. fusca may nest fairly close to a wood-ant mound but is likely to show reduced abundances in terms of nest density and forager number, and, ultimately, lowered fitness.     

鸳鸯利用城市建筑物繁殖初步观察

鸳鸯(Aix galericulata)主要在我国东北地区繁殖,常在树洞里营巢.2008年7月,在广西桂林市城区发现鸳鸯利用居民厨房的通风道繁殖,产卵10枚,并孵出2只幼雏.这是鸳鸯利用建筑物营巢繁殖的首次记录,也是广西繁殖鸟类的新纪录.     

Mechanisms of colony selection by first‐year Lesser Kestrels Falco naumanni

In colonial species, first‐time breeders may use the number of settled conspecifics in colony selection, but such a relationship is confused by the correlation between colony size and nest‐site availability. To distinguish conspecific attraction from neutral colony selection, we experimentally increased nest availability for first‐year Lesser Kestrels Falco naumanni, allowing us to dissociate the number of vacant nest‐sites from colony size at the arrival time of first‐year birds. Under natural conditions, the number of first‐year birds settling was positively correlated with both the number of philopatric and the total number of breeding pairs (colony size) already settled. However, the probability of occupation of experimentally manipulated nests by first‐year birds was independent of colony size. In experimental colonies, the number of first‐year birds settling was positively correlated with the number of manipulated nest‐sites but not with the number of conspecifics. Overall, these results support a neutral colony selection by first‐year Lesser Kestrels based on nest‐site availability.     

A portable system for continuous monitoring of bird nests using digital video recorders

ABSTRACT.   A variety of photographic methods have been described for monitoring nest predation. All have limitations for studying active nests in remote situations, such as size, expense, volume of data recorded, and types of trigger mechanisms. We developed a digital video surveillance system using infrared cameras to monitor predation at bird nests. The main advantage of this system over other video recorders is the small size of the recorder that can run continuously at 29 frames/s for more than 3 days. The recorder's built-in monitor makes it more transportable and allows for easy setup. Digital data is compact, can be reviewed quickly, and requires less physical storage space than videotapes. We recorded nest predation by mammals, birds, and snakes as well as egg and nestling losses not caused by predation. System failure rates were low and the total cost was comparable to ($700 US) video cassette recorders that are often used to monitor nests.     

Influence of a raised slatted area in front of the nest on leg health,mating behaviour and floor eggs in broiler breeders

European farms for broiler breeders often have raised slatted areas in front of the nests, but in other regions of the world no raised slatted areas are provided. This study aimed to investigate the effects of a raised slatted area on leg health, mating behaviour and floor laying behaviour. Ten groups of 33 broiler breeder hens and three males were housed in two pen types: with or without a raised slatted area in front of the nests. Each pen had one plastic and one wooden nest. Between 25 and 31 weeks of age, ten marked hens per pen were weighed and assessed weekly on foot pad dermatitis, hock burn and wounds. At the end of week 31, animals were euthanized and bone strength of the tibia and humerus of these individuals was assessed. At 24, 27 and 30 weeks of age, mating behaviour was observed for an hour per pen, noting both numbers of successful and unsuccessful copulations. The number of eggs laid in the nests and on the floor was recorded daily between 20 and 31 weeks of age. Foot pad dermatitis scores were affected by age, but not by pen type. Generally, there were only minor issues with foot pad dermatitis (scores < 11 on a 0–100 scale), probably due to the young age of the hens. Body weight was not affected by pen type, while the prevalence of hock burns was too low to analyse and no difference in bone strength was found for the tibia and the humerus. Overall, mating behaviour was less frequent in pens with raised slats than in pens without raised slats (29 ± 2 vs 35 ± 3 times/h) and more frequent at 27 weeks of age than at 24 and 30 weeks of age (38 ± 1 vs 31 ± 4 and 27 ± 2 times/h). The pens with raised slats had a lower percentage of floor eggs than pens without raised slats (11.2 ± 0.4 vs 19.3 ± 0.5%). The wooden nest was preferred over the plastic nest as on average 63% of the eggs were laid in the wooden nest. This study shows that providing raised slats decreases mating behaviour and percentage of floor eggs, although its effects on leg health remain inconclusive.     

THE ROLE OF LARGE-SCALE DATA COLLECTION PROJECTS IN THE STUDY OF SOUTHERN AFRICAN BIRDS

Underhill, L.G., Oatley, T.B. & Harrison, J.A. 1991. The role of large-scale data collection projects in the study of southern African birds. Ostrich 62:124-148.

The major ornithological data collections in southern Africa (checklists, migration enquiry, atlas projects, censuses, bird ringing and recoveries, biometric data, nest record cards, moult cards and beached birds) are described. For each project, current volumes of data are tabulated. The Southern African Bird Atlas Project database contained 5,0 million records in December 1990. 1,25 million birds of 810 species had been ringed with South African Bird Ringing Unit rings by June 1989, resulting in 22 000 recoveries. There were more than 100 recoveries for 27 species. The nest record card scheme of the Southern African Ornithological Society had 117 000 cards on file in February 1990, representing 696 species, with more than 1 000 cards for 18 species. There were 4 040 cards of 380 species in the moult record scheme. African Seabird Group beach patrols had found 10 057 seabirds by the end of 1985. A selection of published applications for each data set is given. The potential of the data sets for further analyses is considered, especially in relation to key demographic characteristics such as abundance, productivity and survival. It is recommended that volunteer participation projects should concentrate on monitoring and that indices for change in the demographic characteristics be developed. Most of the projects could be incorporated into an Avian Demography Unit.     

Demographic consequences of nestbox use for Red‐footed Falcons Falco vespertinus in Central Asia

Nestbox programmes are frequently implemented for the conservation of cavity‐nesting birds, but their effectiveness is rarely evaluated in comparison with birds not using nestboxes. In the European Palaearctic, Red‐footed Falcon Falco vespertinus populations are both of high conservation concern and are strongly associated with nestbox programmes in heavily managed landscapes. We used a 21‐year monitoring dataset collected on 753 nesting attempts by Red‐footed Falcons in unmanaged natural or semi‐natural habitats to provide basic information on this poorly known species; to evaluate long‐term demographic trends within this population; and to evaluate response of demographic parameters of Red‐footed Falcons to environmental factors including use of nestboxes. We observed significant differences among years in laying date, offspring loss and numbers of fledglings produced, but not in egg production. Of these four parameters, offspring loss and, to a lesser extent, number of fledglings exhibited directional trends over time. Variation in laying date and in numbers of eggs were not well explained by any one model of environmental factors, but instead by combinations of models, each with informative terms for nest type. Nevertheless, laying in nestboxes occurred 2.10 ± 0.70 days earlier than in natural nests. In contrast, variation in both offspring loss and numbers of fledglings produced were fairly well explained by a single model including terms for nest type, nest location and an interaction between the two parameters (65 and 81% model weights, respectively), with highest offspring loss in nestboxes on forest edges. Because, for other species, earlier laying dates are associated with more fit individuals, this interaction highlighted a possible ecological trap, whereby birds using nestboxes on forest edges lay eggs earlier but suffer greater offspring loss and produce lower numbers of fledglings than do those in other nesting settings. If nestboxes increase offspring loss for Red‐footed Falcons in heavily managed landscapes where populations are at greater risk, or for the many other species of rare or endangered birds supported by nestbox programmes, these processes could have important demographic and conservation consequences.     

Use of passive radio frequency identification technologies to monitor nest usage in the northern carmine bee‐eater (Merops n. nubicus)

The use of radio frequency identification (RFID) technology is common in animal‐monitoring applications in the wild and in zoological and agricultural settings. RFID is used to track animals and to collect information about movements and other behaviors, as well as to automate or improve husbandry. Disney's Animal Kingdom® uses passive RFID technology to monitor nest usage by a breeding colony of northern carmine bee‐eaters. We implemented RFID technologies in various equipment configurations, initially deploying low‐frequency (LF) 125 kHz RFID and later changing to high‐frequency (HF) 13.56 MHz RFID technology, to monitor breeding behavior in the flock. We installed antennas connected to RFID readers at the entrances of nest tunnels to detect RFID transponders attached to leg bands as birds entered and exited tunnels. Both LF‐RFID and HF‐RFID systems allowed the characterization of nest visitation, including the timing of nest activity, breeding pair formation, identification of egg‐laying females, participation by nonresidents, and detection of nest disruptions. However, we collected a substantially larger volume of data using the increased bandwidth and polling speed inherent with HF‐RFID, which permitted tag capture of multiple birds simultaneously and resulted in fewer missed nest visits in comparison to LF‐RFID. Herein, we describe the evolution of the RFID setups used to monitor nest usage for more than 7 years, the types of data that can be gained using RFID at nests, and how we used these data to gain insights into carmine bee‐eater breeding behavior and improve husbandry.     

Displays of the Honeyeater Manorina melanocephala

Investigated displays of Noisy Miners, Manorina melanocephala, in Australia. This unusual bird lives in colonies and many ♂♂ care for the offspring of each ♀ flight displays, 11 non-flight displays, and several components of facial displays (including a variable eye patch) are described. The eye patch provides a large yellow and black augmented eye, important in intimidation. No stereotyped sequence of courtship behaviour precedes copulation. Displays are used to advertise nest locations. A greeting display, the corrohoree, is extremely common. The possibility of the evolution of submissive display from threat is discussed. Special vocalisations of ♂♂ and ♀♀ are use in a duet. The maintenance of bonds among many individuals in a colony may be more important than strong pair bonds. Group cohesion is probably maintained by flight display, nest display, mobbing, and other communal activities. High interspecific aggression results in few resident species in colonies. This level of interspecific aggression might be maintained by incorporating much intraspecific mimetic display and ritualised submissive behaviour.     

Of fleas and geese: the impact of an increasing nest ectoparasite on reproductive success

Past studies on the relationship between nest ectoparasites and avian fitness have been primarily limited to altricial hosts. Life history strategies of precocial and altricial birds vary considerably, limiting our ability to infer the effect of nest parasites on fitness of precocial species. Ross's Chen rossii and lesser snow goose Chen caerulescens caerulescens populations have been growing at unprecedented high rates. New limiting factors on vital rates of these precocial birds may arise after populations have been released from previously regulating factors. The flea Ceratophyllus vagabundus vagabundus is an apparently newly emerging nest parasite in the arctic goose colony at Karrak Lake, Nunavut, Canada. We examined the relationship between flea abundance (measured by the proportion of goose eggs covered by blood in each nest) and goose reproductive success from 2001–2004. In three of four years of study, nest success was inversely related to flea abundance in nests. Despite the potential for high costs to individuals, the overall effects of fleas on goose nesting success have thus far been small. We demonstrated that nest parasites negatively influence reproductive success of precocial bird hosts despite host life history strategy of leaving the nest quickly after hatch, which results in minimal exposure to nest parasites compared to altricial birds that raise their young in the nest.     

Development of flight performance in the brown booby

How do birds acquire flight skills after fledging? This issue is important, as it is closely related to variation in the duration of offspring care, the causes of which remain unknown. In this study, we raised hatchling brown boobies, Sula leucogaster, and attached an acceleration data logger to each bird at fledging to record its movements. This allowed us to quantify precisely the time spent flapping, gliding and resting. The duration of foraging trips and proportion of time spent gliding during flight increased with the number of days since fledging, whereas the proportion of time spent in flight decreased. This indicates that brown boobies gradually acquire efficient flight skills during the post-fledging period, which might be the proximate cause of the long postfledging care period in this species. To the authors' knowledge, this is the first study to record precisely the ontogeny of flight behaviour in birds.     

Nest Defence of Nesting Chinstrap Penguins (Pygoscelis antarctica) against Intruders

We tested some predictions of parental investment theory by studying the aggressive behaviour of colonial nesting chinstrap penguins (Pygoscelis antarctica) against human intruders into their nesting territories. We tested for differences in the aggressive behaviour of penguins according to offspring age (eggs vs. chicks), offspring number, nest location in the colonies (central vs. peripheral) and sex. Offspring age was the main factor influencing nest defence, although nest location and sex were also important. Chicks were defended more strongly than eggs, in accordance with changes in the reproductive value of offspring, and this increase in aggressiveness was not related to revisitation of the same individuals. The level of aggression of penguins breeding in central sites was higher than that of peripheral birds, a difference that could be due to the lower residual reproductive value of central-nesting, probably older, birds. The stronger aggressiveness of males could be due to a combination of factors related to sexual selection and life-history traits. Offspring number did not affect the level of nest defence.     

Breeding success and nest site stereotypy in a population of Brewer's Blackbirds (Euphagus cyanocephalus)

Summary Nest site stereotypy and nest-site related breeding success was studied in a population of Brewer's Blackbirds in eastern Washington, USA. Four types of nest sites could be distinguished. Based on individually colour-ringed nestlings, imprinting or genetic fixation of a particular type of nest site can be ruled out since there is no correspondence between the type of nest a bird grew up in and the type it used when breeding. Bush nests make up about two thirds of all nests, and they are relatively more frequent than the other types in the first half of the breeding season, whereas the other types become more frequent in the second half of the nesting season. Differential breeding success was studied and its dependence on colony composition was investigated.The hypothesis that the birds are able to utilize nest site flexibility as an anti-predator strategy within colonies is not supported. Some nest sites are predictably less suitable at a particular time of the season, and the birds have been at least partially able to incorporate this into their nest-site selection behaviour. There is no optimal type of nest site for all conditions. The selective pressures on birds using the different types of nest sites are discussed.     

Dynamics of the abundance of seagulls (Charadriiformes: Laridae) in the northern Tatar Strait

Field observations on colonies of seagulls (Laridae) were carried out annually on islands of the northern Tatar Strait during 2001–2008. A general tendency towards a reduction in the number of nesting birds was observed on all islands surveyed. The anxiety factor and direct destruction of bird eggs and fledglings caused the whole or the greater part of colony to migrate to “quieter” sites on islands or the continental coast. The replacement of Larus crassirostris by L. schistisagus was observed in sites where the two species nest in neighborhood. Nesting specimens of L. schistisagus were found on islands of Lake Bolshoe Kizi, suggesting that the birds are in search of alternative nesting places that are less accessible to humans and predators.     

FACTORS AFFECTING THE AGE OF FIRST BREEDING OF THE KITTIWAKE RISSA TRIDACTYLA

At a Kittiwake colony in Northumberland, 80% of those birds which returned to their natal colony to breed were males and these supplied 52% of all male recruits. More females breed away from their natal colony than males. There was no differences in the proportions of young fledged from sites in the centre or at the edge of the colony, or by parents of different experience, which returned to breed. Kittiwakes breed for the first time at ages from 3 to 8 years, but most at 4 or S years old. Males arrive back at the colony at an earlier age than females and breed for the first time one year earlier. Males obtaining sites at the centre of the colony first breed at an earlier age than those at the edges. Neither the age nor the area of first breeding appear to be transmitted from parent to offspring. Males breeding first aged 4 years or younger produced more young than those which first bred aged 5 years or older, despite their partners laying smaller clutches. This difference was most marked among those males recruited to sites in the centre of the colony. The advantage of this earlier breeding is counteracted by a lower survival rate among those males which start to breed at the younger ages. In all breeding Kittiwakes, annual reproductive output increases with experience while annual survival rates decrease. Once they had started to breed, many birds failed to breed in one subsequent season. Nearly 60% of these cases of intermittent breeding occurred in the year following first breeding. Intermittent breeding was most frequent among young birds and among females. It is suggested that each breeding involves a cost to the individual in terms of reduced survival, and that deferred and intermittent breeding are means of guarding survival. A model is proposed whereby the age at which a bird starts to breed, the nesting site which it obtains, and its subsequent breeding strategy result in each individual producing an optimal number of reproducing offspring in its lifetime, relative to its quality.     

AGONISTIC AND SPACING BEHAVIOUR OF THE NOISY MINER MANORINA MELANOCEPHALA, A COMMUNALLY BREEDING HONEYEATER

The Noisy Miner is a communally breeding Australian honeyeater in which several males feed the offspring of a single female. They reside year-round in colonies, which may number several hundred birds. Miners within colonies unite to mob predators and are successful in defending their colony area against all other species of birds. The species is also highly aggressive intraspecifically. Individuals in a colony in southeastern Queensland were present most of the time in small activity spaces. Most resident males showed extensive overlap of activity space from one season to the next. Males did not defend their activity spaces, so that coalitions of birds occurred whose membership changed with place and time. Certain assemblages of males, termed coteries, were of a more permanent nature. Coterie members showed aggression towards outsiders at border regions. Females' activity spaces were much smaller and less variable than those of males. They showed almost no overlap and were probably maintained by mutual avoidance. Females tended to nest within the activity space they occupied shortly before the breeding period. Thus the spacing of males and females within a colony was quite different. Interactions, often agonistic, were frequent between individuals, between an individual and a group, and between groups. Encounters involving two males in which participants normally lived farther apart were more often agonistic than when participants lived more closely, and more aggression was seen within coteries than between them. When larger groups of birds had agonistic encounters, they more frequently involved birds from different coteries. Very little male-female aggression was seen. Interactions between males and females of different coteries were usually sexual, sometimes involving attempted copulation. Colony sizes are probably too large to permit individual recognition of fellow members, but this could be more likely in coteries. Many males in coteries are doubtless closely related, but outsiders frequently infiltrate them. Coteries are not reproductive units.     

Nourishment affects colony demographics in the paper wasp Polistes metricus

Abstract  1. Colony survivorship and numbers of nest cells, pupae, and adult females were monitored throughout the nesting season for a cohort of 78 colonies of the paper wasp Polistes metricus Say. Thirty-nine colonies received a twice-weekly nourishment supplement of honey during pre-emergence and early emergence phases of the colony cycle; 39 colonies were unsupplemented controls.
2. Colony survivorship was unaffected by the supplemental nourishment. Loss of colonies to predation differed among three sites but was unaffected by supplementation.
3. Honey-supplemented colonies constructed more nest cells than did control colonies but this effect was not expressed until after supplementation had ceased.
4. Honey-supplemented colonies produced more pupae than did control colonies but the number of adult females at nests did not differ between supplemented and control colonies. Because honey-supplemented colonies had more offspring but fewer of them remained as workers at the nest, honey supplementation led to a lower frequency of workers and corresponding higher frequency of reproductives than in control colonies.
5. In a second year of study, colony survivorship and numbers of nest cells, pupae, and adult females were monitored from late pre-emergence until the end of the nesting season for a cohort of 32 colonies of Polistes metricus . In 16 colonies, trophallactic saliva was taken from final-instar larvae on nine dates in the late pre-emergence and early emergence periods; 16 colonies served as controls.
6. Saliva-diminished colonies had lower survivorship, fewer nest cells, fewer pupae, and fewer adult females at the nest than did control colonies.
7. These results show that variation in nourishment in the early to mid phases of the colony cycle can have significant effects on the subsequent colony demographics of Polistes metricus paper wasps.     

Effects of reproductive timing and colony size on the survival, offspring colony size and drone production in the honey bee (Apis mellifera)

ABSTRACT. 1. The effects of colony size and time of reproduction on the survival and size of offspring colonies and on drone production were examined for honey bees, Apis mellifera L. Drone and worker production and survival of parental and offspring colonies were monitored following swarming. Also, the temporal patterns of drone emergence and availability of unmated queens were examined.
2. Colony size at swarming was positively correlated with the number of workers invested in offspring colonies and the number of queens produced. However, colony size at swarming was not correlated with the number of offspring colonies produced.
3. Swarm size was positively correlated with drone and worker production after swarms were hived. Worker production of hived swarms was positively correlated with colony survival. Offspring queens which inherited a parental nest survived longer than queens in either primary swarms or afterswarms, presumably due to the advantage of inheriting a nest.
4. Drone emergence peaked just prior to swarming, the time when unmated queens were available. High drone production by colonies initiated by swarms probably reflected an attempt to reproduce prior to winter. The probabilities of a second swarming cycle within the same year and of surviving the winter were low for colonies initiated from swarms.