How far will a behaviourally flexible invasive bird go to innovate?

Behavioural flexibility is considered a key factor in the ability to adapt to changing environments. A traditional way of characterizing behavioural flexibility is to determine whether individuals invent solutions to novel problems, termed innovativeness. Great-tailed grackles are behaviourally flexible in that they can change their preferences when a task changes using existing behaviours; however, it is unknown how far they will go to invent solutions to novel problems. To begin to answer this question, I gave grackles two novel tests that a variety of other species can perform: stick tool use and string pulling. No grackle used a stick to access out-of-reach food, even after seeing a human demonstrate the solution. No grackle spontaneously pulled a vertically oriented string, but one did pull a horizontally oriented string twice. Additionally, a third novel test was previously conducted on these individuals and it was found that no grackle spontaneously dropped stones down a platform apparatus to release food, but six out of eight did become proficient after training. These results support the idea that behavioural flexibility is a multi-faceted trait because grackles are flexible, but not particularly innovative. This contradicts the idea that behavioural flexibility and innovativeness are interchangeable terms.SAGE Center for the Study of the Mind (University of California Santa Barbara)This is the final version. It first appeared from Royal Society Publishing at http://dx.doi.org/10.1098/rsos.160247

Temporal and Individual Variation in Offspring Provisioning by Tree Swallows: A New Method of Automated Nest Attendance Monitoring

Studies of the ecology and evolution of avian nesting behavior have been limited by the difficulty and expense of sampling nest attendance behavior across entire days or throughout a substantial portion of the nestling period. Direct observation of nesting birds using human observers and most automated devices requires sub-sampling of the nestling period, which does not allow for the quantification of the duration of chick-feeding by parents within a day, and may also inadequately capture temporal variation in the rate at which chicks are fed. Here I describe an inexpensive device, the Automated Perch Recorder (APR) system, which collects accurate, long-term data on hourly rates of nest visitation, the duration of a pair's workday, and the total number of visits the pair makes to their nest across the entire period for which it is deployed. I also describe methods for verifying the accuracy of the system in the field, and several examples of how these data can be used to explore the causes of variation in and tradeoffs between the rate at which birds feed their chicks and the total length of time birds spend feeding chicks in a day

Dynamics in numbers of group-roosting individuals in relation to pair-sleeping occurrence and onset of egg-laying in European Bee-eaters Merops apiaster

Sleeping in the nest at the beginning of the breeding season is common for birds nesting in cavities. Here, we report evidence that European Bee-eaters Merops apiaster sleep in pairs in the nesting burrow. In 3.2 % of the nest checks we found two individuals sleeping together. This behaviour ceased once hatching started. A decrease in the number of birds at a communal roost coincided with the incidences of pair-sleeping and initiation of egg-laying. Thus, checking the burrows of European Bee-eaters at beginning of the breeding season increases the chance of observing pair-sleeping

Contrast in Edge Vegetation Structure Modifies the Predation Risk of Natural Ground Nests in an Agricultural Landscape

Nest predation risk generally increases nearer forest-field edges in agricultural landscapes. However, few studies test whether differences in edge contrast (i.e. hard versus soft edges based on vegetation structure and height) affect edge-related predation patterns and if such patterns are related to changes in nest conspicuousness between incubation and nestling feeding. Using data on 923 nesting attempts we analyse factors influencing nest predation risk at different edge types in an agricultural landscape of a ground-cavity breeding bird species, the Northern Wheatear (Oenanthe oenanthe). As for many other bird species, nest predation is a major determinant of reproductive success in this migratory passerine. Nest predation risk was higher closer to woodland and crop field edges, but only when these were hard edges in terms of ground vegetation structure (clear contrast between tall vs short ground vegetation). No such edge effect was observed at soft edges where adjacent habitats had tall ground vegetation (crop, ungrazed grassland). This edge effect on nest predation risk was evident during the incubation stage but not the nestling feeding stage. Since wheatear nests are depredated by ground-living animals our results demonstrate: (i) that edge effects depend on edge contrast, (ii) that edge-related nest predation patterns vary across the breeding period probably resulting from changes in parental activity at the nest between the incubation and nestling feeding stage. Edge effects should be put in the context of the nest predator community as illustrated by the elevated nest predation risk at hard but not soft habitat edges when an edge is defined in terms of ground vegetation. These results thus can potentially explain previously observed variations in edge-related nest predation risk

Introduced Mammalian Predators Induce Behavioural Changes in Parental Care in an Endemic New Zealand Bird

The introduction of predatory mammals to oceanic islands has led to the extinction of many endemic birds. Although introduced predators should favour changes that reduce predation risk in surviving bird species, the ability of island birds to respond to such novel changes remains unstudied. We tested whether novel predation risk imposed by introduced mammalian predators has altered the parental behaviour of the endemic New Zealand bellbird (Anthornis melanura). We examined parental behaviour of bellbirds at three woodland sites in New Zealand that differed in predation risk: 1) a mainland site with exotic predators present (high predation risk), 2) a mainland site with exotic predators experimentally removed (low risk recently) and, 3) an off-shore island where exotic predators were never introduced (low risk always). We also compared parental behaviour of bellbirds with two closely related Tasmanian honeyeaters (Phylidonyris spp.) that evolved with native nest predators (high risk always). Increased nest predation risk has been postulated to favour reduced parental activity, and we tested whether island bellbirds responded to variation in predation risk. We found that females spent more time on the nest per incubating bout with increased risk of predation, a strategy that minimised activity at the nest during incubation. Parental activity during the nestling period, measured as number of feeding visits/hr, also decreased with increasing nest predation risk across sites, and was lowest among the honeyeaters in Tasmania that evolved with native predators. These results demonstrate that some island birds are able to respond to increased risk of predation by novel predators in ways that appear adaptive. We suggest that conservation efforts may be more effective if they take advantage of the ability of island birds to respond to novel predators, especially when the elimination of exotic predators is not possible

Facultative polyandry and the role of infant-carrying in wild saddle-back tamarins ( Saguinus fuscicollis )

Wild saddle-back tamarins ( Saguinus fuscicollis ) in southeastern Peru have a variable mating system that can differ both between territories at any one time and within territories over time. Groups are usually monogamous or cooperatively polyandrous, but are occasionally even polygynous. This study addressed the following questions: why does this population contain both monogamous and polyandrous groups simultaneously? What factors determine whether specific groups are monogamous or polyandrous? The data from this study population tentatively support the hypothesis that adults should mate monogramously only if they have nonreproductive helpers (usually older offspring) to help rear infants. Without helpers, the reproductive success of both males and females is hypothesized to be higher, on average, if they mate polyandrously than if they mate monogamously. The proposed benefits of polyandry to males and females differ quantitatively, but in both cases benefits stem from the help that males provide in rearing young. The following results support this hypothesis. (1) Lone pairs were never seen to attempt breeding, and calculations suggest that the costs of lactation and infant-carrying are too great for lone pairs to have a high probability of being able to raise twin offspring (the normal litter size). (2) Polyandrous males and nonreproductive offspring contributed substantially to infant care, particularly infant-carrying (fig. 2). (3) Adult males carried infants approximately twice as often as did lactating females, presumably because of the combined costs of (a) lactation (Fig. 3) and (b) infant-carrying (Fig. 4). The proximate causes of cooperative polyandry in S. fuscicollis appear to be different from those responsible in several bird species, showing that cooperative polyandry is a complex phenomenon.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/46876/1/265_2004_Article_BF00572631.pd

Cooperative breeding by the Galápagos mockingbird, Nesomimus parvulus

The costs and benefits of helping behavior were analyzed for 36 pairs of the Galápagos mockingbird, Nesomimus parvulus , and their associates. Helping at the nest is usually done by sons or males suspected to be offspring of the breeders. Costs and benefits to breeders were assessed by comparison of pairs with and without helpers, and costs and benefits to helpers were assessed by comparison of birds which help and those which establish themselves as novice breeders.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/46866/1/265_2004_Article_BF00296397.pd

On the mating system of the cooperatively breeding saddle-backed tamarin ( Saguinus fuscicollis )

This paper reports on 5 years of observatiors of individually marked saddle-backed tamarins ( Saguinus fuscicollis , Callitrichidae). Although callitrichids have long been presumed to have a monogamous social system, this study shows that the breeding structure of saddle-back tamarin groups is highly variable. Groups most commonly include two or more adult males and a single reproductive female, but occasionally contain only a single pair of adults, or less often, two reproductively active females and one or more males. Data on group compositions, group formations, intergroup movements and copulations show that the social and mating systems of this species are more flexible than those of any other non-human primate yet studied. Infants (usually twins) were cared for by all group members. There were two classes of helpers: young, nonreproductive individuals who helped to care for full or half siblings, and cooperatively polyandrous males who cared for infants whom they may have fathered. The observations suggest that non-reproductive helpers may benefit from their helping behavior through a combination of inclusive fitness gains, reciprocal altruism, and the value of gaining experience at parental care.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/46874/1/265_2004_Article_BF00295541.pd

Geographic variation in social organization of Galápagos mockingbirds: ecological correlates of group territoriality and cooperative breeding

To investigate ecological influences on cooperative social organization, I studied the four allopatric species of mockingbirds ( Nesomimus spp.) endemic to the Galápagos archipelago on four islands. On three small, low and arid islands (Genovesa, Champion and Española), mockingbird territories filled all terrestrial habitat, mean group size varied from 4.5 to 14.2 adults, maximum group size ranged from seven to 24 birds, and 70–100% of groups contained more than two birds. San Cristóbal is larger and higher, and it supports a broader range of habitats. At one highland and two coastal sites on this island, mockingbirds did not hold territories in all available habitats, group size averaged 2.2 adults, only 25% of groups were larger than two, and none included more than three adults. Adults dispersed into vacant habitat to establish new territories only on San Cristóbal. Helping behavior has not yet been observed on San Cristóbal, but it occurs on the other three islands. These results support the hypothesis that social groups and cooperative breeding are maintained where limited availability of preferred habitat constrains dispersal. The mechanism relaxing habitat saturation on San Cristóbal, however, remains undetermined. Predation by introduced rats and cats may reduce survival and indirectly reduce group size; these predators are absent from Genovesa, Champion and Española. Differences in food supplies could also affect interand intra-island variation in population density. Variation in social organization among arid coastal sites on the four islands, and similarity between climatically different sites on San Cristóbal, suggest that climatic conditions are less important as determinants of dispersal and breeding. Skews in adult sex ratios also fail to account for inter-island variation in sociality. Although they live in a climatically variable environment, territorial behavior and the physical limits of suitable habitat have an overriding influence on cooperative social organization in Galápagos mockingbirds.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/46894/1/265_2004_Article_BF00302932.pd