Temporal Variability and cooperative Breeding: Testing the Bet-Hedging Hypothesis in the Acorn Woodpecker

Cooperative breeding is generally considered an adaptation to ecological constraints on dispersal and independent breeding, usually due to limited breeding opportunities. Although benefits of cooperative breeding are typically thought of in terms of increased mean reproductive success, it has recently been proposed that this phenomenonmay be a bet-hedging strategy that reduces variance in reproductive success (fecundity variance) inpopulations living inhighly variable environments. We tested this hypothesis using long-term data on the polygynandrous acorn woodpecker (Melanerpes formicivorus). In general, fecundity variance decreased with increasing sociality, at least when controlling for annual variation in ecological conditions. Nonetheless, decreased fecundity variance was insufficient to compensate for reduced per capita reproductive success of larger,more social groups, which typically suffered lower estimatedmean fitness.We did, however, find evidence that sociality in the form of larger group size resulted in increased fitness in years following a small acorn crop due to reduced fecundity variance. Bet-hedging, although not the factor driving sociality in general, may play a role in driving acorn woodpecker group living when acorns are scarce and ecological conditions are poor

Variable Helper Effects, Ecological Conditions, and the Evolution of Cooperative Breeding in the Acorn Woodpecker

The ecological conditions leading to delayed dispersal and helping behavior are generally thought to follow one of two contrasting scenarios: that conditions are stable and predictable, resulting in young being ecologically forced to remain as helpers (extrinsic constraints and the habitat saturation hypothesis), or that conditions are highly variable and unpredictable, leading to the need for helpers to raise young, at least when conditions are poor (intrinsic constraints and the hard life hypothesis). We investigated how variability in ecological conditions influences the degree to which helpers augment breeder fitness in the cooperatively breeding acorn woodpecker (Melanerpes formicivorus), a species in which the acorn crop, territory quality, and prior breeding experience all vary in ways that have important effects on fitness. We found that the relationship between ecological conditions and the probability that birds would remain as helpers was variable but that helpers generally yielded greater fitness benefits when ecological conditions were favorable, rather than unfavorable, for breeding. These results affirm the importance of extrinsic constraints to delayed dispersal and cooperative breeding in this species, despite its dependence on a highly variable and unpredictable acorn crop. Our findings also confirm that helpers can have very different fitness effects, depending on conditions, but that those effects are not necessarily greater when breeding conditions are unfavorable

Cooperative Breeding and Long-Distance Dispersal: A Test Using Vagrant Records

Cooperative breeding is generally associated with increased philopatry and sedentariness, presumably because short-distance dispersal facilitates the maintenance of kin groups. There are, however, few data on long-distance dispersal in cooperative breeders-the variable likely to be important for genetic diversification and speciation. We tested the hypothesis that cooperative breeders are less likely to engage in long-distance dispersal events by comparing records of vagrants outside their normal geographic range for matched pairs (cooperatively vs. non-cooperatively breeding) of North American species of birds. Results failed to support the hypothesis of reduced long-distance dispersal among cooperative breeders. Thus, our results counter the conclusion that the lower rate of speciation among cooperative breeding taxa found in recent analyses is a consequence of reduced vagility

Seasonal Forecast Based Preharvest Hedging

Given the immense effect of weather on agriculture, skillful weather forecasts are of importance to agricultural producers for effective decision making. Weather forecasts affect operational decisions such as whether or not to irrigate (where applicable), when to apply fertilizer, when to spray herbicide and pesticide, and certainly the timing of planting and harvesting. At the seasonal time scale, say in the spring, just before planting, weather forecasts may be used for strategic decision making on outcomes, say from preharvest hedging (hereafter referred to hedging), that will not be realized until the fall or harvest. Historically, the lack of skill in generating seasonal forecasts has led the vast majority of agricultural producers to not have enough confidence to use weather forecasts in the hedging decision. Scientific advancements improving skill and accuracy of seasonal weather forecasts in the 21st century have occurred due to a better understanding of the interplay between atmosphere, land, and oceans, as well as faster and more detailed computer analysis of weather and climate data (Benjamin et al., 2018). Yet, the adoption of weather forecasts in decision making in the agricultural sector has remained low. According to Klemm and McPherson (2018), the lack of adoption of forecasts can be attributed due in part to a lack of stakeholder relevance of the forecast information, a lack of forecast accuracy, or simply because the forecasts are too difficult to understand. The goal of this paper is to motivate the use of a modern-day weather forecast in the hedging decision. We achieve this goal by investigating how modern-day weather forecasts are established and develop a simple hedging model based on the weather forecast

Testing Alternative Hypotheses for the Cause of Population Declines: The Case of the Red-Headed Woodpecker

The Red-headed Woodpecker (Melanerpes erythrocephalus) has experienced strong population declines during the past 3 decades. Using North American Breeding Bird Survey (BBS) and Audubon Christmas Bird Count (CBC) data, we investigated 4 hypotheses that may explain this decline, including: (1) interspecific competition with native Red-bellied Woodpeckers (Melanerpes carolinus) and nonnative European Starlings (Sturnus vulgaris); (2) predation by Cooper\u27s Hawks (Accipiter cooperii) and Sharp-shinned Hawks (Accipiter striatus); (3) climate change; and (4) changes in forested area within their range. In analyses of both the breeding and overwintering periods, our results indicated a role of increased accipiter populations in driving Red-headed Woodpecker declines through increased predation. We also found evidence for significant effects of warmer winter temperatures and increased forest cover, both directly and indirectly through their effects on enhancing accipiter populations. In contrast, our results failed to support the hypothesis that interspecific competition with either Red-bellied Woodpeckers or European Starlings has played a role in Red-headed Woodpecker declines. Despite considerable evidence for nest-site competition and aggression between Red-headed Woodpeckers and both Red-bellied Woodpeckers and European Starlings, these interactions do not appear to be limiting Red-headed Woodpecker populations

Habitat Saturation Results in Joint-Nesting Female Coalitions in a Social Bird

Joint nesting by females and cooperative polyandry—cooperatively breeding groups with a male-biased breeder sex ratio—are little-understood, rare breeding systems. We tested alternative hypotheses of factors potentially driving these phenomena in a population of joint-nesting acorn woodpeckers (Melanerpes formicivorus). During periods of high population density and thus low independent breeding opportunities, acorn woodpecker females formed joint-nesting coalitions with close kin. Coalitions were typically associated with groups with a male bias. We found strong evidence for both inter- and intrasexual conflict, as joint nesting conferred a fitness benefit to some males, a significant fitness cost to females, and no gain in per capita reproductive output for either sex. Such conflict, particularly the cost to females, may be an important reason why joint nesting is rare among cooperatively breeding taxa

Territory Inheritance and the Evolution of Cooperative Breeding in the Acorn Woodpecker

There are two main hypotheses for why offspring in cooperatively breeding taxa delay dispersal and remain on their natal territory rather than disperse. First, ecological constraints may force offspring to remain on their natal territory until a reproductive opportunity presents itself in an otherwise saturated habitat. Alternatively, delaying dispersal and helping kin may increase an offspring\u27s inclusive fitness. One means by which offspring might enhance their direct fitness by delaying dispersal is by inheriting breeding status on their natal territory. Such territory inheritance regularly occurs in acorn woodpeckers, Melanerpes formicivorus, a species whose social groups consist of a cooperatively polygynandrous breeding core along with nonbreeding helpers of both sexes that are offspring from prior breeding efforts. Here we examine the life-history differences and the fitness consequences of birds attaining breeder status by either inheriting their natal territory or dispersing to a new territory. Despite significant differences in life history, including the mean territory quality on which individuals bred and mean co-breeder coalition size of breeders, we found no statistical differences in either direct or kin-selected (indirect) fitness benefits for breeders that inherited and dispersed. The incidence of birds engaging in both strategies, inheriting their natal territory and later dispersing, or dispersing but later returning to inherit their natal territory, further reduces the potential direct fitness benefits of inheritance relative to dispersal, since neither precludes the other. Territory inheritance is an important, alternative means of achieving breeding status in this population. However, ecological constraints to dispersal and kin-selected fitness benefits as a helper likely play larger roles driving the acorn woodpecker\u27s extraordinary social system

Lifetime Reproductive Benefits of Cooperative Polygamy Vary for Males and Females in the Acorn Woodpecker (\u3ci\u3eMelanerpes formicivorus\u3c/i\u3e)

Cooperative breeding strategies lead to short-term direct fitness losses when individuals forfeit or share reproduction. The direct fitness benefits of cooperative strategies are often delayed and difficult to quantify, requiring data on lifetime reproduction. Here, we use a longitudinal dataset to examine the lifetime reproductive success of cooperative polygamy in acorn woodpeckers (Melanerpes formicivorus), which nest as lone pairs or share reproduction with same-sex cobreeders. We found that males and females produced fewer young per successful nesting attempt when sharing reproduction. However, males nesting in duos and trios had longer reproductive lifespans, more lifetime nesting attempts and higher lifetime reproductive success than those breeding alone. For females, cobreeding in duos increased reproductive lifespan so the lifetime reproductive success of females nesting in duos was comparable to those nesting alone and higher than those nesting in trios. These results suggest that for male duos and trios, reproductive success alone may provide sufficient fitness benefits to explain the presence of cooperative polygamy, and the benefits of cobreeding as a duo in females are higher than previously assumed. Lifetime individual fitness data are crucial to reveal the full costs and benefits of cooperative polygamy