Behavioral Ecology of Tropical Birds

By Bridget J.M. Stutchbury and Eugene S. Morton

Behavioral Ecology of Tropical Birds, Second Edition provides the most updated and comprehensive review on the evolution of behavior in tropical landbirds. The book reviews gaps in our knowledge that were identified twenty years ago when the first edition was published, highlights recent discoveries that have filled those gaps, and identifies new areas in urgent need of study. It covers key topics, including timing of breeding, movement ecology, life history traits, slow vs. fast pace of life, mating systems, mate choice, territoriality, communication, biotic interactions, and conservation.

Written by international experts on the behavior of tropical birds, the book explores why the tropics is a unique natural laboratory to study the evolution of bird behavior and why temperate zone species are so different. A recent surge of studies on tropical birds has helped to reduce the temperate zone bias that arose because most avian model species in behavioral ecology were adapted to northern temperate climates. This is an important resource for researchers, ecologists and conservationists who want to understand the rich and complex evolutionary history of avian behavior.

• Includes examples from around the world
• Provides a historical perspective on new knowledge in the past 20 years
• Identifies knowledge gaps that have been filled, along with new gaps that have emerged
• Explores how avian behavior in the tropics is related to conservation

• Language: English
• Publisher: Academic Press
• Release date: Sep 28, 2022
• ISBN: 9780128238158

Bridget J.M. Stutchbury

Bridget Stutchbury is a Distinguished Research Professor of Biology at York University in Toronto, Canada. She is an internationally recognized expert on songbird behavior, migration, and conservation. She and her graduate students have studied mating systems, communication, and territory defense in a range of resident passerines in Panama, as well as the non-breeding ecology of migrants in Mexico, Belize, and Costa Rica. She has also published numerous papers on the behavioral ecology of temperate-breeding passerines and she pioneered the use of light-level geolocators to track start-to-finish long distance migration of small birds. Dr. Stutchbury is the recipient of numerous research awards, including a Canada Research Chair award, the Margaret Morse Nice Award for lifetime achievement from the Wilson Ornithological Society, the Elliott Coues Award for outstanding and innovative contributions to ornithological research from the American Ornithological Society, and the Jamie Smith Memorial Mentoring Award from the Society of Canadian Ornithology.

Book preview

9780128238158_FC

Behavioral Ecology of Tropical Birds

Second Edition

Bridget J.M. Stutchbury

Department of Biology, York University, Toronto, ON, Canada

Eugene S. Morton

Smithsonian Conservation Biology Institute National Zoological Park, Smithsonian Institution, Washington, DC, United States

Table of Contents

Cover image

Title page

Copyright

Preface

References

Chapter 1: Why are tropical birds interesting?

Abstract

1.1: Ecology and breeding seasons

1.2: Species diversity

1.3: Behavioral diversity in tropical birds

References

Chapter 2: Timing of breeding

Abstract

2.1: Seasonality in tropical breeding seasons

2.2: Food availability and timing of breeding

2.3: Nest predation and feather molt

2.4: Optimal timing of breeding and fitness

References

Chapter 3: Life history traits

Abstract

3.1: High adult and juvenile survival

3.2: High Nest predation

3.3: Small clutch size

3.4: Slow pace of life and physiology

References

Chapter 4: Mating systems

Abstract

4.1: Monogamy, sex role convergence, and mate choice

4.2: Extra-pair mating systems: Tropics versus temperate zone

4.3: Promiscuity

4.4: Cooperative breeding

References

Chapter 5: Territoriality

Abstract

5.1: Territory systems

5.2: Territory defense

5.3: Testosterone

5.4: Territory acquisition

5.5: Territory switching and divorce

5.6: Territory quality and individual fitness

References

Chapter 6: Intratropical and altitudinal migration

Abstract

6.1: Intratropical migration

6.2: Altitudinal migration

References

Chapter 7: Communication

Abstract

7.1: The assessment/management concept in communication

7.2: Song, territoriality and extra-pair behavior

7.3: Sex role convergence in song and duetting

7.4: Song ranging, neighborhood stability, and dialects

7.5: Plumage signals

References

Chapter 8: Biotic interactions

Abstract

8.1: Birds and plants

8.2: Avoiding predators

8.3: Mixed-species flocks

8.4: Interspecific competition

8.5: What biotic interactions mean to the conservation of tropical birds

References

Chapter 9: Behavior and conservation

Abstract

9.1: Tropical bird declines

9.2: Gap-crossing and dispersal in fragmented landscapes

9.3: Habitat fragmentation, nesting success, and source-sink dynamics

9.4: Intratropical and altitudinal migration

9.5: Climate change

References

Chapter 10: Conclusion: Is the temperate zone bias still a problem?

Abstract

10.1: Previous knowledge gaps that are now better filled

10.2: New topics in behavioral ecology

10.3: Current knowledge gaps

References

References

Index

Copyright

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Preface

Our first edition was written as a call to arms, and we hoped it would inspire an army of graduate students and researchers, from the temperate zone and the tropics, to set out to study the behavioral ecology of tropical birds before it was too late to document their amazing adaptations and diversity. We include almost 300 references on tropical birds in this second edition that were published after 2001, and of course there are many more excellent studies that we did not have room to mention. These twenty years of research efforts on tropical birds have filled many gaps in our knowledge (e.g., extra-pair mating systems and duetting), have introduced new and already well-studied concepts (e.g., pace of life), and have raised new questions and concerns (e.g., intratropical migration, behavior and conservation).

The premise for our book is nicely captured by Alexander Skutch (1985) who wrote that the important question is not Why do tropical birds lay so few eggs? Rather, it is Why do temperate-zone birds lay so many? We had seen this temperate zone bias in many areas of avian behavioral ecology, including the evolution of extra-pair mating systems, female territory defense, and how song is used in communication. Most studies were based on temperate zone species that share a lifestyle of social monogamy, seasonal territoriality, high territory and mate competition in spring, and a short breeding season. In the tropics, the varied breeding seasons, diet, territory systems, importance of mate choice, and biotic interactions create selection pressures and evolutionary outcomes that are far more diverse. Opportunities still abound for describing, discovering, and discussing the beautiful ways tropical birds are different from run-of-the-mill temperate zone birds and from each other.

Tropical birds, especially year-round residents, are fundamentally challenging to study. Breeding seasons can be eight months long and nest predation very high, making it hard to measure individual productivity and determine long-term effects of experiments (e.g., food supplantation, brood manipulation, and territory owner removal). The relative shortage of studies on tropical birds compared with temperate-breeding birds is also for logistical reasons. For researchers based in tropical countries, limited research funding may constrain the scale of the research and the number of researchers (Reboreda et al., 2019). For temperate zone biologists, field work in the tropics can be challenging because it is more expensive, more time-consuming, and more physically demanding than working in the temperate zone spring and summer. Many temperate zone professors and students must be on their home campus for most of the year for teaching and course work or may have family responsibilities that curtail long-term and long-distance travel. We have written this second edition vicariously, having not done intensive field work in Panama for over 10 years. Though unintended, this second edition became our pandemic project, and we would have preferred to be in the tropics for at least part of its creation.

The tropics are famous for the abundance and complexity of biotic interactions of relationships such as predator-prey, parasite-host, mutualisms, and competition. These have led to wondrous adaptations and specializations (e.g., wasps that live inside figs, caterpillar larvae that look like bird poop, and antbirds that follow ants), but biotic interactions can also make life somewhat miserable for the biologists who work there. Along with our graduate students, our experiences with field work in the tropics include contracting diseases such as the flesh-eating Leishmaniasis parasite introduced through the bite of a sand fly and Dengue, the RNA virus that is spread by mosquitoes. Many of us have been parasitized by bot flies whose larva grow just under your skin getting more painful by the day as it wriggles around and comes up for air. Bridget is unfortunately very sensitive to chiggers, which are almost invisible larval mites, whose initial harmless bite develops into itchy and oozing red swellings that number in the dozens on any given day. One graduate student poked an eye with a stinging Mala Mujer plant and had to rush back to Canada, while another who had developed a mysterious allergy to beef mistakenly ate some on the flight home and could barely stumble through customs. Although some of our students who worked in the tropics never went back, others never left.

We thank Virginia Benjamen, a York University graduate and our research assistant, who helped enormously with editing, literature searches, content creation, and administrative tasks. Funding was provided through York University and a grant to BJMS from the Natural Sciences and Engineering Research Council of Canada.

Bridget J.M. Stutchbury

Eugene S. Morton

References☆

Skutch, 1985 Skutch A.F. Clutch size, nesting success, and predation on nests of neotropical birds, reviewed. In: Buckley P.A., Foster M.S., Morton E.S., Ridgely R.S., Buckley F.G., eds. Neotropical Ornithology. Washington, DC: The American Ornithologists' Union; 575–594. 1985;vol. 36.

Reboreda, Fiorini and Tuero, 2019 Reboreda J.C., Fiorini V.D., Tuero E.T., eds. Behavioral Ecology of Neotropical Birds. Springer; 2019.

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☆ To view the full reference list for the book, click here

Chapter 1: Why are tropical birds interesting?

Abstract

Tropical birds are interesting because they are so different from typical temperate zone birds upon which the overwhelming amount of research in avian behavioral ecology has been based. Although stark temperate-tropical differences in life history traits, such as clutch size and lifespan, have intrigued ecologists for decades, far less attention has been paid to other aspects of behavioral ecology. Tropical birds provide endless ways to test behavioral ecology hypotheses because their behavior, and their ecology, is far more diverse than typical temperate zone birds. The factors driving timing of breeding are far more varied in the tropics and different species breed at opposite times of the year. The selection pressures that influence parental care, territoriality, mating systems, and migration within the tropics are also highly varied. Biodiversity peaks in the tropics and so does the importance of biotic interactions such as mixed-species flocks and bird-plant specializations. Tropical habitats are facing among the world’s highest rates of degradation and loss, yet the natural history of many tropical birds remains unstudied. We urgently need to fill the gaps in behavioral ecology studies of tropical birds before we lose the chance to understand the rich evolutionary history that has created this behavioral diversity.

Keywords

Seasonality; Biodiversity; Duetting; Lekking; Ant-following; Migration

1.1: Ecology and breeding seasons

For many people, a tropical bird brings to mind a spectacular toucan or parrot, and, for the more ornithologically minded, other charismatic birds like motmots, manakins, and antbirds. These are birds that cannot be seen in the northern temperate zone. One might imagine oneself in a lush rainforest with towering trees, hanging vines, and branches choked with bromeliads while being serenaded by bird song aplenty, interrupted by the occasional distant bellowing of howler monkeys. While this is the habitat that tourists and bird watchers flock to, many tropical birds specialize on other places like mangrove, cloud forest, savannah, and dry forest. Many species are elevational specialists and are adapted to only a narrow range of elevations, such that the bird community changes quickly over short distances up- versus downhill. Some of the lesser-known and plain-looking tropical birds, like woodcreepers and flycatchers, have very high numbers of species. The number of different tropical bird species in one place can be overwhelming. It is a simple matter, especially during the dry season, to show a first-time visitor to the tropics six dozen species of birds in their first morning, as we have done many times in the lowland forests of central Panama. Even a very small country like Panama has about 900 species of birds (Ridgely and Gwynne, 1992), more than all of the United States and Canada!

Not as fully appreciated are the fundamental differences in ecology that tropical birds experience. There is no such thing as winter in the tropics, which in the temperate zone comes with depressingly short daylength and some bitterly cold temperatures. Spring-like weather in the temperate zone arrives fairly predictably year to year, deviating by only a few weeks early or late, because of steadily increasing daylength. Even a winter storm in mid-March can be assured to be followed by warmer days and imminent emergence of plant and insect life. The tropical year is divided into the dry versus wet season, and not the spring, summer, fall, and winter. Although the tropics have relatively constant day length and daytime temperature year-round, this does not mean that the birds that live there enjoy a stable and predictable environment. Most species live year-round on the same small territory, or home range, where they experience long periods of deluges, then drought, across the year. Some species breed only in the wet season and others only in the dry season. In the Western Hemisphere, the tropical wet season often occurs roughly from May to November north of the equator, and below the equator at the opposite time of year. In East Africa, the timing of the wet season also varies strongly with latitude and there are two wet seasons near the equator (Fig. 1.1A, e.g., Wrege and Emlen, 1991).

Fig. 1.1

Fig. 1.1 (A) Timing of the wet season (shaded) in east Africa at different latitudes and times of the year. (B) Length of the dry season (days) in central Panama from 1977 to 2011. (A: Redrawn from Moreau, R.E., 1950. The breeding seasons of African birds. 1. Land birds. Ibis 92, 223–267; B: Data from Brawn, J.D., Benson, T.J., Stager, M., Sly, N.D., Tarwater, C.E., 2017. Impacts of changing rainfall regime on the demography of tropical birds. Nat. Clim. Chang. 7, https://doi.org/10.1038/nclimate3183.)

Even in the same location, the timing and duration of dry and wet seasons in the tropics are extremely variable across years. In central Panama, for instance, the length of the dry season can be six months long in one year but only three months in another (Fig. 1.1B). Tropical birds have evolved high behavioral plasticity in timing of breeding and reproductive effort to live with this very unpredictable seasonality (Martin and Mouton, 2020). Because of this seasonality, year-round residents face trade-offs in when to undertake energetically expensive activities like breeding versus feather molt. For instance, Hawaii Akepa (Loxops coccineus coccineus) parents overfeed their nestlings because food is so abundant during nesting, and this fat storage allows the fledglings to survive the next few months when parents are molting and food is scarce (Freed et al., 2007).

The great majority of north temperate species migrate south to warmer, food-rich, regions during the nonbreeding season, whereas most tropical-breeding birds are year-round residents. The temperate zone spring brings a massive surge of insect food for birds, much of it in the form of easy-to-catch and protein-rich insect larvae that are perfect for raising a large brood of rapidly growing altricial nestlings (Fig. 1.2A). Temperate zone plants tend to fruit after the birds’ breeding season, when adults and juveniles begin dispersing and migrating making them better seed dispersers for the plants. Though temperate zone passerines rely on insect food for breeding, many switch to a largely frugivorous diet in late summer when fruit is abundant (e.g., Scarlet Tanager Piranga olivacea, Rose-breasted Grosbeak Pheucticus ludovicianus, and Red-eyed Vireo Vireo olivacea). In the tropics, plants often invest in chemical defense of their leaves, which are not shed annually, and so insect food for birds is often in the form of hard-to-catch adult insects, which are available year-round depending on the severity of the dry season (Fig 1.2B). Fruiting plants compete for pollinators and dispersers and stagger their fruiting times, so fruit can be found at any time of year and many tropical birds eat almost exclusively fruit (e.g., manakins and cotingas) but still need insect food for feeding nestlings. Year-round food allows most tropical birds to be sedentary although other species are seasonally territorial and many migrate annually within the tropics.

Fig. 1.2

Fig. 1.2 Insect (open bars) and fruit (solid circles) abundance over the year in (A) the northern temperate zone ( Holmes et al., 1986; Thompson and Willson, 1979) versus (B) tropics ( Levey, 1988; Young, 1994).

The temperate spring involves males arriving en masse, over just a few weeks, to set up territories and attract mates. This overlaps with later-arriving females that select a mate/territory and soon after lay their first clutch of eggs. The competition is fierce, and the stakes are high because the chances of surviving to try again the next breeding season are low. This sets the stage for major temperate-tropical differences in social behavior (extra-pair mating system, territorial behavior, sex roles, and singing), physiology (testosterone), and life history traits (clutch size, fledgling care period, timing of juvenile dispersal, and adult survival). On the life history continuum, migratory temperate zone birds live a fast pace of life (low survival and high reproductive effort), while tropical resident birds live a slow pace of life (high survival, low reproductive effort, and low metabolic rate). Behavioral ecology hypotheses developed for temperate breeding birds may not be well suited to explain tropical adaptions (Reboreda et al., 2019).

1.2: Species diversity

Most biologists recognize biodiversity as the most obvious, and important, difference between temperate and tropical birds. It has long been known that bird species diversity increases dramatically in the tropics and part of the mystique of the tropics is the continual discovery of new species, and the rediscovery of species long thought to be extinct (Lees et al., 2020). About 300 new bird species have been described worldwide since 1950, and almost all have been tropical birds (Jenkins et al., 2013). Globally, the highest diversity of birds is found in tropical rainforests that include the Amazon, Brazilian Atlantic Forest, Congo, Eastern Africa, and Southeast Asia (Jenkins et al., 2013). For instance, there is only one genus of hummingbird in eastern North America, but over 25 in the tropics. Similarly, there are only five genera of tyrant flycatchers in eastern Canada and the United States, but a remarkable 79 genera in Brazil (Fig. 1.3). Antbirds are totally absent in northern latitudes but are highly diverse in Panama and Brazil. Hypotheses for high species richness in tropical regions include a faster speciation rate due to habitat and elevational specialization, complex biotic interactions, and/or a longer time over which species have accumulated. About one in three Neotropical bird species is a suboscine (e.g., flycatchers, antbirds, woodcreepers, and manakins), a group that has undergone incredible adaptive radiation. Phylogenetic analysis of the suboscines found no evidence of a higher speciation rate in the Neotropics, and instead, the high diversity is a result of slow and steady accumulation of new species over millions of years (Harvey et al., 2020).

Fig. 1.3

Fig. 1.3 Number of genera within each family at five different locations in the Western Hemisphere (eastern Canada, southeastern United States, Mexico, Panama, and Brazil). Families are Accipitridae (hawks, eagles, and kites), Trochilidae (hummingbirds), Tyrannidae (flycatchers), and Formicariidae (antbirds).

Anyone who has visited tropical regions has witnessed the massive deforestation, with endless miles of pastures and fields where giant trees once stood shoulder to shoulder. Tropical forests are being destroyed so quickly that even basic information on what species once lived there is often not known. Hundreds of tropical studies in recent decades have focused on documenting patterns of bird diversity at regional and global scales (Araneda et al., 2018; Lees et al., 2020) often as part of a strategic biodiversity assessment to identify priorities for habitat conservation (e.g., biodiversity hotspots). A tiny area (7% of global land surface) is home to 50% of all the world’s birds which you might think would make it easier to protect these 5000 or so species from being threatened with extinction. Unfortunately, these same regions are under intense pressure to support large and growing human populations and only 10% of this land area has strict protection (Jenkins et al., 2013). Long-term studies have shown species losses and population declines in both intact forest (Brawn et al., 2017; Curtis et al., 2021) and agricultural landscapes (Sekercioglu et al., 2019). There is great interest in how agricultural land use can better support bird diversity (Karp et al., 2011). For instance, more sustainable agroforestry (e.g., cocoa and coffee plantations) can be achieved for birds by providing higher canopy cover and shade trees (Bennett et al., 2021; Philpott and Bichier, 2012). This is a rare win-win scenario because the greater diversity and abundance of birds reduce insect pests and increase crop production (Martínez-Salina et al., 2016; Philpott et al., 2009).

1.3: Behavioral diversity in tropical birds

But another kind of diversity is important too, and that is the amazing behavioral diversity in adaptations among tropical birds. Tropical birds offer unique opportunities to test ecological and evolutionary theory for behavioral traits because their seasonality, diet, biotic interactions, and territorial and migratory behavior are often so extremely different from a typical temperate zone species. Despite the fact that 80% of passerine birds reside in tropical latitudes, behavioral ecology studies of birds are dominated by the minority of temperate-breeding birds many of whom share a common suite of behavioral adaptations that are imposed by the northern climate and short breeding season. Most north temperate passerines defend seasonal breeding territories, males are far more territorial than females, extra-pair paternity is common, between-year divorce is the norm, reproductive effort is high, and annual survival is low. For north temperate passerines, it seems clear that individuals time their egg-laying so food for raising young will be abundant, sexual selection is strong even in socially monogamous species because of the extra-pair mating system, the evolution of song is driven by sexual selection, and testosterone underlies male territorial aggression and mate attraction. Much theory in avian behavioral ecology comes from models and empirical studies of birds in north temperate regions, in part because so many well-funded researchers are based at universities in North America and Europe and do their research locally. Some of these researchers, and their students, may not even realize that the conventional wisdom developed for temperate-breeding birds does not apply so well to tropical birds that live with very different selection pressures. Because of their worldwide dominance, tropical birds should be considered the norm when it comes to behavioral adaptations, but instead temperate zone birds are used overwhelmingly to test and develop new ideas. This is what we call the temperate zone bias (Stutchbury and Morton, 2001).

Researchers that are based at institutions in tropical regions are among the strongest voices calling for behavioral ecology hypotheses to be tested in, and developed for, tropical birds (Reboreda et al., 2019). Much of the recent behavioral ecology research on tropical birds has been done by researchers and students who are based in tropical countries (e.g., Awade and Metzger, 2008; Araya-Salas et al., 2018; Bravo et al., 2017; Carlo and Morales, 2016; Ferretti, 2019; Guaraldo et al., 2016; Jahn et al., 2016; Macedo and Manica, 2019; Muñoz et al., 2018).

The diversity in behavioral ecology among tropical birds is far greater than within the temperate zone (Tobias et al., 2012a). There are more lekking birds, more cooperatively breeding birds, more fruit and nectar specialists, and more types of territorial systems (e.g., canopy and understory mixed-species flocks, and army ant-following specialists). Within the same study site, there may be species that are territorial and paired year-round, resident year-round but territorial only during the breeding season, and seasonally intratropical or altitudinal migrants. In many tropical passerines, females sing and defend territories vigorously and duetting is more common in the tropics. Biotic interactions are more complex and numerous in the tropics leading to codependencies between individual species of plants and their pollinating or fruit-dispersing birds, and avoidance of interspecific competition among birds had led to specialized bill morphology and foraging behaviors. This diversity is a powerful tool for testing behavioral ecology theory and developing new ideas that have a broad evolutionary scope.

Behavioral ecology has certainly not ignored the adaptations of tropical birds; for instance, hypotheses for the small clutch size and the varied breeding seasons of tropical birds date back over fifty years. Temperate-tropical comparisons have a long and rich history in behavioral ecology and have been applied most frequently to questions such as timing of breeding (Chapter 2), life history evolution (e.g., survival, clutch size, and parental investment; Chapter 3), mating systems (lekking and cooperative breeding; Chapter 4), song (e.g., duetting; Chapter 7), and biotic interactions (pollination, frugivory, and mixed-species flocks; Chapter 8). For instance, Tieleman et al. (2006) compared House Wrens Troglodytes aedon breeding in Panama versus Ohio and found the tropical resident population had a higher annual survival, invested less energy in reproduction (e.g., lower field metabolic rate and smaller clutch size), and had a longer breeding season. The tropics is still often viewed as a place to go study oddities like lekking, ant-following, and duetting rather than to focus on run-of-the-mill socially monogamous birds (Tobias et al., 2012a,b). But it is the latter that allows for a more rigorous and apples-to-apples comparison of temperate versus tropical adaptations.

One of the largest and most important gaps for the behavioral ecology of tropical birds is basic natural history, as many species have not been the subject of any intensive study. Basic is in quotation marks because such natural history details are a prerequisite to understanding the behavioral ecology of any species, and there is nothing easy or simple about doing an intensive field study on a tropical bird. Broad comparative studies to test evolutionary hypotheses rely on data mining population-level studies to test predictions, but behavioral variables (e.g., timing of egg-laying, territory size, song rate, extent of parental care, nestling growth rate, fledgling survival, juvenile survival, and dispersal timing and distance) are available for only a tiny percentage of tropical birds. Many such tropical studies have been done in the Neotropics, with far less known about tropical birds from elsewhere. For many key behaviors, we do not yet understand variation among tropical species, let alone why temperate and tropical species differ. For instance, we generally do not know why adult survival varies within and among tropical birds, to what extent high reproductive effort reduces future fecundity or survival, how socially monogamous species choose mates and whether this is important to lifetime fitness, whether territory quality affects reproductive success or survival, or why extra-pair paternity varies so greatly among tropical birds. While migration tracking has exploded for temperate zone migrants (McKinnon and Love, 2018), there are only a handful of migration tracking studies for intratropical or altitudinal tropical migrants. Many of the classic hypothesis-testing experiments that have become standard for temperate birds (e.g., food supplementation, cross-fostering, egg and brood size manipulations, and removal of territory owners) remain scarce for tropical birds (Tobias et al., 2012a,b).

Despite these important gaps in our knowledge (Stutchbury and Morton, 2001), hundreds of studies have been published on the behavioral ecology of tropical birds in the past twenty years. This second edition updates all the major topics of our first book and includes major new conceptual and empirical advances (e.g., pace of life; Chapter 3). We also include a review of migration behavior within the tropics (Chapter 6) and consider how behavioral adaptations will help, or hinder, conservation efforts considering massive habitat loss and climate change (Chapter 9). We conclude by reviewing the major gaps in knowledge that we identified in our first edition to see whether these have now been filled (many have not!) and what new gaps have emerged (Chapter 10; Table 10.1). Although research effort on tropical birds has increased greatly, in part because of urgent conservation needs, the temperate zone bias in behavioral ecology persists for many key questions.

References☆

Ridgely R.S., Gwynne J.A. A Guide to the Birds of Panama: With Costa Rica, Nicaragua, and Honduras. Princeton, NJ: Princeton University Press; 1992.

Wrege P.H., Emlen S.T. Breeding seasonality and reproductive success of White-fronted Bee-eaters in Kenya. Auk. 1991;108:673–687.

Martin T.E., Mouton J.C. Longer-lived tropical songbirds reduce breeding activity as they buffer impacts of drought. Nat. Clim. Chang. 2020;10:953–958.

Freed L.A., Fretz J.S., Medeiros M.C. Adaptation in the Hawaii akepa to breed and moult during a seasonal food decline. Evol. Ecol. Res. 2007;9:157–167.

Reboreda, Fiorini and Tuero, 2019 Reboreda J.C., Fiorini V.D., Tuero E.T., eds. Behavioral Ecology of Neotropical Birds. Springer; 2019.

Lees C.A., Rosenberg K.V., Ruiz-Gutierrez V., Marsden S., Schulenberg T.S., Rodewald A.D. A roadmap to identifying and filling shortfalls in neotropical ornithology. Auk. 2020;137:1–17.

Jenkins C.M., Pimm S.L., Joppa L.N. Global patterns of terrestrial vertebrate diversity and conservation. Proc. Natl. Acad. Sci. 2013;110(28):E2602–E2610. doi:10.1073/pnas.1302251110.

Harvey M.G., Bravo G.A., Claramunt S. The evolution of a tropical biodiversity hotspot. Science. 2020;370:1343–1348.

Araneda P., Sielfeld W., Bonacic C., Ibarra J.T. Bird diversity along elevational gradients in the Dry Tropical Andes of northern Chile: the potential role of Aymara indigenous traditional agriculture. PLoS One. 2018;13(12):e0207544doi:10.1371/journal.pone.0207544.

Brawn J.D., Benson T.J., Stager M., Sly N.D., Tarwater C.E. Impacts of changing rainfall regime on the demography of tropical birds. Nat. Clim. Chang. 2017;7:doi:10.1038/nclimate3183.

Curtis J.R., Robinson D., Rompré G., Moore R.P., McCune B. Erosion of tropical bird diversity over a century is influenced by abundance, diet and subtle climatic tolerances. Sci. Rep. 2021;11:10045. doi:10.1038/s41598-021-89496-7.

Sekercioglu C.H., Mendenhall C.D., Oviedo-Brenes F., Horns J.J., Erlich P.R., Daily G.C. Long-term declines in bird populations in tropical agricultural countryside. Proc. Natl. Acad. Sci. 2019;116(20):9903–9912.

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