Walter D. Koenig

University of California, Berkeley | UCB · Museum of Vertebrate Zoology

Mast seeding, the synchronous and highly variable production of seed crops by perennial plants, is a population‐level phenomenon and has cascading effects in ecosystems. Mast seeding studies are typically conducted at the population/species level. Much less is known about synchrony in mast seeding between species because the necessary long‐term dat...

Plants display a range of temporal patterns of inter‐annual reproduction, from relatively constant seed production to “mast seeding,” the synchronized and highly variable interannual seed production of plants within a population. Previous efforts have compiled global records of seed production in long‐lived plants to gain insight into seed producti...

Offspring that delay dispersal in cooperatively breeding species have been hypothesized to gain direct fitness benefits via parental facilitation—being passively tolerated on their natal territory by their parents—thereby enjoying enhanced survival and increased probability of acquiring a breeding position in the population. Here we describe active...

Offspring that delay dispersal in cooperatively breeding species have been hypothesized to gain direct fitness benefits via parental facilitation—being passively tolerated on their natal territory by their parents—thereby enjoying enhanced survival and increased probability of acquiring a breeding position in the population. Here we describe active...

Although over 50 y have passed since W. D. Hamilton articulated kin selection and inclusive fitness as evolutionary explanations for altruistic behavior, quantifying inclusive fitness continues to be challenging. Here, using 30 y of data and two alternative methods, we outline an approach to measure lifetime inclusive fitness effects of cooperative...

Context Spatial occupancy and local abundance of species often positively covary, but the mechanisms driving this widespread relationship are poorly understood. Resource dynamics and habitat changes have been suggested as potential drivers, but long-term studies relating them to abundance and occupancy are rare. In this 34-year study of acorn woodp...

The drivers of year-to-year difference in winter abundance patterns, particularly dramatic in the “eruptions” of many boreal seed-eating birds, are poorly understood. Varied Thrush (Ixoreus naevius (Gmelin, 1789)), endemic to the Pacific Northwest of North America, is a boreal species that exhibits pronounced, often biennially cyclic, changes in wi...

Wood-decay fungi soften wood, putatively providing opportunities for woodpeckers to excavate an otherwise hard substrate, yet the fungal community composition in tree cavities and the specificity of these relationships is largely unknown. We used high-throughput amplicon sequencing of the fungal ITS2 region to examine the fungal communities associa...

Significant gaps remain in understanding the response of plant reproduction to environmental change. This is partly because measuring reproduction in long-lived plants requires direct observation over many years and such datasets have rarely been made publicly available. Here we introduce MASTREE+, a dataset that collates reproductive time-series d...

Significance Suitable habitats for forest trees may be shifting fast with recent climate change. Studies tracking the shift in suitable habitat for forests have been inconclusive, in part because responses in tree fecundity and seedling establishment can diverge. Analysis of both components at a continental scale reveals a poleward migration of nor...

We studied the timing of budburst of valley oak (Quercus lobata Ne) at Hastings Reservation, central coastal California. Similar to other taxa, budburst was advanced by warmer temperatures. Over the 30-year study period, however, there were no significant trends in either air temperature or the timing of budburst, except during the 20142016 drought...

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 coope...

Despite its importance for forest regeneration, food webs, and human economies, changes in tree fecundity with tree size and age remain largely unknown. The allometric increase with tree diameter assumed in ecological models would substantially overestimate seed contributions from large trees if fecundity eventually declines with size. Current esti...

Although primary cavity-nesting species are capable of excavating new cavities, they often reuse old ones. To determine potential factors driving such reuse, we studied nest-cavity reuse in the Acorn Woodpecker (Melanerpes formicivorus), a cooperatively breeding species that reuses old cavities for 57.2% of nests at Hastings Reservation in central...

A Correction to this paper has been published: https://doi.org/10.1038/s41467-021-22025-2

Indirect climate effects on tree fecundity that come through variation in size and growth (climate-condition interactions) are not currently part of models used to predict future forests. Trends in species abundances predicted from meta-analyses and species distribution models will be misleading if they depend on the conditions of individuals. Here...

Triadic awareness, or knowledge of the relationships between others, is essential to navigating many complex social interactions. While some animals maintain relationships with former group members post-dispersal, recognizing cross-group relationships between others may be more cognitively challenging than simply recognizing relationships between m...

In species with long-term social relationships, the ability to recognize individuals after extended separation and the ability to discriminate between former social affiliates that have died and those that have left the group but may return are likely to be beneficial. Few studies, however, have investigated whether animals can make these discrimin...

With automated telemetry, Barve et al. tracked cooperatively breeding acorn woodpeckers during ‘power struggles’—complex conflicts wherein ‘warrior’ birds fight for breeding positions as ‘spectator’ birds watched. Telemetry was used to quantify effort expended by warriors gaining territories and spectators receiving social information.

Quantifying masting behavior—the highly variable, yet synchronized, production of seeds by forest trees and other plants—is of considerable importance to ecosystem function and forest management, yet typically requires years of study to acquire. In contrast, measuring radial growth by mean of tree-ring cores potentially yields decades or more of da...

Masting behavior — variable and synchronized reproduction by a population of plants — has long been recognized as correlating with weather. How and why weather conditions influence seed production is, however, poorly understood. We investigated the relationships between acorn production and both local weather and long-term climate in 10 populations...

Interannual variability of seed crops (CVp) has profound consequences for plant populations and food webs, where high CVp is termed ‘masting’. Here we ask: is global variation in CVp better predicted by plant or habitat differences consistent with adaptive economies of scale, in which flower and seed benefits increase disproportionately during mast...

Resource pulses are rare events with a short duration and high magnitude that drive the dynamics of both plant and animal populations and communities¹. Mast seeding is perhaps the most common type of resource pulse that occurs in terrestrial ecosystems², is characterized by the synchronous and highly variable production of seed crops by a populatio...

Ecological processes, such as migration and phenology, are strongly influenced by climate variability. Studying these processes often relies on associating observations of animals and plants with climate indices, such as the El Niño–Southern Oscillation (ENSO). A common characteristic of climate indices is the simultaneous emergence of opposite ext...

What factors drive population variability through space and time? Here we assess patterns of abundance of seven species of gall wasps in three genera occurring on the leaves of valley oaks ( Quercus lobata ) at 10 sites throughout this species' statewide range in California, from 2000 to 2006. Our primary goals were to understand the factors drivin...

In many cooperatively breeding taxa, nonbreeding subordinates, or helpers, use extra‐territorial forays to discover dispersal opportunities. Such forays are considered energetically costly and foraying birds face aggression from conspecific members of the territories they visit. In contrast, breeders in cooperatively breeding taxa are expected to f...

Highly variable and synchronised production of seeds by plant populations, known as masting, is implicated in many important ecological processes, but how it arises remains poorly understood. The lack of experimental studies prevents underlying mechanisms from being explicitly tested, and thereby precludes meaningful predictions on the consequences...

Mast seeding is one of the most intriguing reproductive traits in nature. Despite its potential drawbacks in terms of fitness, the widespread existence of this phenomenon suggests that it should have evolutionary advantages under certain circumstances. Using a global dataset of seed production time series for 219 plant species from all of the conti...

Cooperative breeding groups often involve “helpers-at-the-nest”; indeed, such behavior typically defines this intriguing breeding system. In few cases, however, has it been demonstrated that feeding nestlings by helpers, rather than some other behavior associated with helpers' presence, leads to greater reproductive success. One prediction of the h...

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 pop...

Trees are commonly thought to increase their seed production before death. We tested this terminal investment hypothesis using long-term data on rowan trees ( Sorbus aucuparia ) and found no support. Rather, seed production declined significantly before death, which points to the potential detrimental effects of reproductive senescence on regenerat...

Premise of the study: The influence of weather conditions on masting and the ecological advantages of this reproductive behavior have been the subject of much interest. Weather conditions act as cues influencing reproduction of individual plants, and similar responses expressed across many individuals lead to population-level synchrony in reproduc...

Seed dispersal and predation play important roles in plant life history by contributing to recruitment patterns in the landscape. Mast-seeding extensive synchronized inter-annual variability in seed production is known to-in uence the activity of acorn consumers at source trees, but little is known about its e ect on post-dispersal fl ff predation....

Clutch size and reproductive success decline seasonally in a wide range of temperate avian taxa. Two competing hypotheses have been proposed to explain such declines: the “timing” hypothesis, which states that conditions affecting reproduction decline intrinsically with date, and the “quality” hypothesis, which proposes that high‐quality individual...

According to the social intelligence hypothesis, understanding the cognitive demands of the social environment is key to understanding the evolution of intelligence. Many important socio-cognitive abilities, however, have primarily been studied in a narrow subset of the social environment-within-group social interactions-despite the fact that betwe...

Mistletoes are a widespread group of plants often considered to be hemiparasitic, having detrimental effects on growth and survival of their hosts. We studied the effects of the Pacific mistletoe, Phoradendron villosum, a member of a largely autotrophic genus, on three species of deciduous California oaks. We found no effects of mistletoe presence...

We investigated the role of species- and community-wide seed production by a community of oaks (Quercus spp.) in influencing tree attendance and aggression among California scrub-jays (Aphelocoma californica), corvids that are seed dispersal mutualists, and acorn woodpeckers (Melanerpes formicivorus), near-exclusive seed predators. We tested the hy...

Mast seeding, or masting, is the highly variable and spatially synchronous production of seeds bya population of plants. The production of variable seed crops is typically correlated with weather, so it is of considerable interest whether global climate change has altered the variability ofmasting or the size ofmasting events. We compiled 1086 data...

We investigated spatial synchrony of acorn production by valley oaks (Quercus lobata) among individual trees at the within-population, local level and at the among-population, statewide level spanning the geographic range of the species. At the local level, the main drivers of spatial synchrony were water availability and flowering phenology of ind...

The emerald ash borer (EAB) Agrilus planipennis, first detected in 2002 in the vicinity of Detroit, Michigan, USA, has spread throughout much of eastern and midwestern North America as of 2016, resulting in widespread mortality of ash trees in the genus Fraxinus. We investigated the effects of this newly available, exotic food source on populations...

Landscape features affect habitat connectivity and patterns of gene flow and hence influence genetic structure among populations. We studied valley oak (Quercus lobata), a threatened species of California (USA) savannas and oak woodlands, with a distribution forming a ring around the Central Valley grasslands. Our main goal was to determine the rol...

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 Woodpec...

The terminal investment hypothesis, which proposes that reproductive investment should increase with age-related declines in reproductive value, has garnered support in a wide range of animal species, but has not been previously examined in long-lived plants such as trees. We tested this hypothesis by comparing relative acorn production and radial...

1. In communities of large-seeded tree species, generalist seed hoarders often link the temporally variable dynamics of various species in ways that can result in indirect ecological interactions. A special case of such interactions is "apparent predation" – when variation in seed production of one tree species changes the outcome of the interactio...

Acorn woodpeckers, Melanerpes formicivorus, are cooperative breeders in which social groups consist of both nonbreeding helpers at the nest (offspring from prior reproductive attempts) and cobreeders of one or both sexes (usually siblings or a parent and his/her offspring). Regardless of composition, groups generally have one nest at a time at whic...

I. II. III. IV. V. VI. VII. VIII. IX. References SUMMARY: Mast seeding is a widespread and widely studied phenomenon. However, the physiological mechanisms that mediate masting events and link them to weather and plant resources are still debated. Here, we explore how masting is affected by plant resource budgets, fruit maturation success, and horm...

Although the functional basis of variable and synchronous seed production (masting behavior) has been extensively investigated, only recently has attention been focused on the proximate mechanisms driving this phenomenon. We analyzed the relationship between weather and acorn production in 15 species of oaks (genus Quercus) from three geographic re...

Avian trichomonosis, a disease typically caused by the protozoan parasite Trichomonas gallinae , is a well recognized cause of death in many avian species. In California, trichomonosis has caused periodic epidemics in Pacific Coast Band-tailed Pigeons ( Patagioenas fasciata monilis). We summarize reported mortality events and investigate ecologic d...

Spatial and temporal variation in resource distribution affect the movement and foraging behavior of many animals. In the case of animal-dispersed trees, numerous studies have addressed masting—the synchronized variation in seed production between years—but the fitness consequences of spatial variation in seed production within a year are unclear....

The ecological impacts of modern global climate change are detectable in a wide variety of phenomena, ranging from shifts in species ranges to changes in community composition and human disease dynamics(1-3). So far, however, little attention has been given to temporal changes in spatial synchrony-the coincident change in abundance or value across...

Seed dispersal mutualisms with scatter-hoarders play a crucial role in population dynamics of temperate large-seeded trees. These behaviors shape seed dispersal patterns, which can be applied to conservation of populations, communities, and even ecosystems dominated by large-seeded trees. We draw on a growing body of literature to describe the ecol...

Cooperative breeders are species in which individuals beyond a pair assist in the production of young in a single brood or litter. Although relatively rare, cooperative breeding is widespread taxonomically and continues to pose challenges to our understanding of the evolution of cooperation and altruistic behavior. Bringing together long-term studi...

Cooperative breeders are species in which individuals beyond a pair assist in the production of young in a single brood or litter. Although relatively rare, cooperative breeding is widespread taxonomically and continues to pose challenges to our understanding of the evolution of cooperation and altruistic behavior. Bringing together long-term studi...

Masting, the synchronized production of variable seed crops, is widespread among woody plants, but there is no consensus about the underlying proximate mechanisms. To understand this population‐level behaviour, it is necessary to dissect the behaviour of individual trees as well as the interactions that synchronize them. Here, we test a model of ma...

Cooperative breeders are species in which individuals beyond a pair assist in the production of young in a single brood or litter. Although relatively rare, cooperative breeding is widespread taxonomically and continues to pose challenges to our understanding of the evolution of cooperation and altruistic behavior. Bringing together long-term studi...

Premise of the study: Although long-distance pollen movement is common in wind-pollinated trees, barriers to gene flow may occur in species that have discontinuous ranges or are confined to certain habitat types. We investigated the genetic structure of Quercus lobata Née populations throughout much of their range in California. We assessed the co...

The Acorn Woodpecker Melanerpes formicivorus is one of a small number of woodpecker species that are cooperative breeders, living in family groups of up to 15 individuals of both sexes and all ages and exhibiting a complex mating system involving multiple cobreeders of both sexes (polygynandry). Although much has been learned concerning the social...

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 phenomenon may be a bet...

Highly variable patterns of seed production (“masting”) have been hypothesized to be driven by internal dynamics of resource storage and depletion. This hypothesis predicts that if seed production is artificially reduced, then the availability of unused stored resources should result in subsequent enhancement of the seed crop. We tested this predic...

Annually variable and synchronous seed production, or masting behavior, is a widespread phenomenon with dramatic effects on wildlife populations and their associated communities. Proximally, masting is often correlated with environmental factors and most likely involves differential pollination success and resource allocation, but little is known a...

1. Plants from different populations often display a variation in herbivore resistance. However, it is rarely understood what plant traits mediate such differences. 2. It was tested how leaf phenology affects herbivore populations in a 15‐year‐old common garden of valley oaks ( Quercus lobata Née) with different populations and maternal parents fro...

Significance This study is the first, to our knowledge, to reveal how climate variability drives irruptions of North American boreal seed-eating birds. Patterns of Pine Siskin irruption and associated climate drivers manifest as two modes (North-South and West-East) in which dipoles of temperature and precipitation anomalies push and pull irruptive...

Forest communities change in response to shifting climate, changing land use, and species introductions, as well as the interactions of established species. We surveyed the oak (Quercus L. spp.) community and Acorn Woodpecker (Melanerpes formicivorus (Swainson, 1827)) population within 230 ha of oak forest and savanna in central coastal California...

Understanding the proximate factors that govern the widespread mast‐seeding process is a question of considerable interest that remains poorly understood. The identity and effect of these factors may vary among coexisting species that differ in leaf habit, potentially resulting in temporally asynchronous patterns of seed production. In this study,...

Pollen limitation is a key assumption of theories that explain mast seeding, which is common among wind-pollinated and woody plants. In particular, the pollen coupling hypothesis and pollination Moran effect hypothesis assume pollen limitation as a factor that synchronizes seed crops across individuals. The existence of pollen limitation has not, h...

The seasonal match between folivore and leaf phenology affects the annual success of arboreal folivore populations because many folivores exploit developing leaves, which are an ephemeral resource. One strategy for folivores to exploit early-season leaves is to anticipate their emergence. The consequence of this behavior for trees is that individua...