Woodpecker Finches Research Articles

Evolutionary divergence of body size and wing and leg structure in relation to foraging mode in Darwin’s Galapagos finches

Abstract The wings, legs, and tail in Darwin’s finches show many clear adaptations to different types of locomotion used during foraging. We use size scaling to analyse how various characters vary with body mass to clarify dimensional relationships. The selective advantage of a character is judged in terms of energy savings. The wing aspect ratio (4.6–4.9) is very low, so the energy costs for flight are high. Low body mass, low wing loading, and short arm wings in the warbler finch, small tree finch, and small ground finch promote agility and manoeuvrability among vegetation, along with short wings in the warbler finch. Evolution towards a shorter arm wing seems to be favoured in the smaller finch species. Long legs, long toes, and long curved claws are adaptations for climbing/clinging locomotion without tail support (woodpecker finch, small and large tree finches, cactus finch but having short legs). Selection for longer legs seems to act towards a lengthening of the tarsometatarsus. The climbing technique in the woodpecker finch is described. We discuss how the diversification in the beaks relates to the locomotion organs.

Slow motion extinction: inbreeding, introgression, and loss in the critically endangered mangrove finch (Camarhynchus heliobates)

The critically endangered mangrove finch is now limited to one small population on the west coast of Isabela Island in the Galapagos, but 100 years ago multiple populations were found on the islands of Isabela and Fernandina. By accessing genetic datasets through museum sampling, we are able to put current levels of genetic diversity and hybridization with congenerics into a historical context for enhanced conservation. In this study, we compared neutral genetic diversity of the now extinct Fernandina population to historical and current diversity of the Isabela population using 14 microsatellite markers. We found that current genetic diversity of the last remnant population (~80–100 individuals) is far below levels 100 years ago, with only about half of the allelic diversity retained. Current genetic diversity is close to levels in the Fernandina population that went extinct by the 1970s. Bottleneck analysis did not show a strong signature of recent decline, and instead implies that this species may have consistently had low population sizes with wide fluctuations. Hybridization with congeneric woodpecker finches was found in the modern Isabela population, implying that some individuals within the few remaining breeding pairs are finding mates with woodpecker finches. Within the context of historical low population sizes and wide fluctuations, current conservation efforts may help the mangrove finch face current extinction threats and avoid the fate of the Fernandina population. However, this historically small lineage will likely continue to face challenges associated with small specialist species surrounded by a widely-distributed sister lineage producing viable hybrids.

Coping with Uncertainty: Woodpecker Finches (Cactospiza pallida) from an Unpredictable Habitat Are More Flexible than Birds from a Stable Habitat

Behavioural flexibility is thought to be a major factor in evolution. It may facilitate the discovery and exploitation of new resources, which in turn may expose populations to novel selective forces and facilitate adaptive radiation. Darwin's finches are a textbook example of adaptive radiation. They are fast learners and show a range of unusual foraging techniques, probably as a result of their flexibility. In this study we aimed to test whether variability of the environment is correlated with flexibility. We compared woodpecker finches from a dry area (hereafter, Arid Zone), where food availability is variable, with individuals from a cloud forest (hereafter, Scalesia zone) where food abundance is stable. As parameters for flexibility, we measured neophilia and neophobia, which are two aspects of reaction to novelty, reversal learning and problem-solving. We found no differences in performance on a problem-solving task but, in line with our prediction, individuals from the Arid Zone were significantly faster reversal learners and more neophilic than their conspecifics from the Scalesia zone. The latter result supports the notion that environmental variability drives flexibility. In contrast to our prediction, Arid Zone birds were even more neophobic than birds from the Scalesia Zone. The latter result could be the consequence of differences in predation pressure between the two vegetation zones.

Did tool-use evolve with enhanced physical cognitive abilities?

The use and manufacture of tools have been considered to be cognitively demanding and thus a possible driving factor in the evolution of intelligence. In this study, we tested the hypothesis that enhanced physical cognitive abilities evolved in conjunction with the use of tools, by comparing the performance of naturally tool-using and non-tool-using species in a suite of physical and general learning tasks. We predicted that the habitually tool-using species, New Caledonian crows and Galápagos woodpecker finches, should outperform their non-tool-using relatives, the small tree finches and the carrion crows in a physical problem but not in general learning tasks. We only found a divergence in the predicted direction for corvids. That only one of our comparisons supports the predictions under this hypothesis might be attributable to different complexities of tool-use in the two tool-using species. A critical evaluation is offered of the conceptual and methodological problems inherent in comparative studies on tool-related cognitive abilities.

Increasing avian pox prevalence varies by species, and with immune function, in Galápagos finches

Avian pox virus (APV), a pathogen implicated as a major factor in avian declines and extinctions in Hawaii, was introduced to the Galápagos in the late 1890s. While APV is thought to have increased in prevalence in recent years, no study has carefully evaluated the threat this pathogen poses to the Galápagos avifauna. In this paper, we examine the course of the APV epidemic in seven species of Galápagos finch on Santa Cruz Island (Geospiza fuliginosa, G. fortis, G. magnirostris, G. scandens, Camarhynchus parvulus, Cactospiza pallida, and Certhidea olivacea). We describe temporal changes in the prevalence of the avian pox disease (AP) caused by APV and the proportion of individuals that have recovered from AP from 2000 to 2009. Then we examine species differences in susceptibility to AP and how this variation correlates with differences in innate immune function. We show that AP prevalence has increased dramatically from 2000 to 2009. However, this increase in prevalence varied by species; specifically, we found that prevalence increased rapidly in G. fuliginosa, C. parvulus, G. scandens, and C. olivacea, but not at all in G. fortis. Furthermore, innate immune function varies between years and species, and this variation correlates with increased prevalence and species variation in susceptibility to APV. To our knowledge, this is the first study to demonstrate significant interannual variation in innate immune function in wild birds, and to show that this immune variation correlates with susceptibility to an introduced disease.

The Relationship Between Foraging, Learning Abilities and Neophobia in Two Species of Darwin’s Finches

AbstractThe ability to unlearn a previously established association is an important component of behavioural flexibility and may vary according to species ecology. Previously, two closely related sympatric Darwin’s finches were found to differ in their learning abilities. Small tree finches (Camarhynchus parvulus) outperformed woodpecker finches (Cactospiza pallida) in reversal learning but performed worse in an operant task. We attributed this difference to the habit of woodpecker finches to engage in long bouts of energetic pecking during extractive foraging. Persistently repeating one action without reward could favour performance in operant tasks but also limit behavioural flexibility. Here, we tested whether perseverance is the reason for woodpecker finches’ depressed reversal learning performance. Two new reversal conditions allowed the disentanglement of two sources of error in reversal learning: perseverant choice of the previously rewarded stimulus and failure to respond to the previously non‐rewarded stimulus. For the within‐species comparison, we predicted that woodpecker finches should find it more difficult to learn to avoid the previously rewarded stimulus than learning to choose the previously non‐rewarded stimulus. For the species comparison, we predicted the woodpecker finches should make more errors of perseverance than small tree finches. As performance could also be influenced by reaction to novelty, we compared neophobic responses between species and related them to reversal learning proficiency. We found no significant difference in reversal learning in the predicted direction, but found a negative correlation between neophobia and reversal learning at the inter‐ and the intraspecific level, which points towards a general relationship between reaction to novelty and flexibility.

Use of a barbed tool by an adult and a juvenile woodpecker finch (Cactospiza pallida)

Here we describe the modification and use of a new tool type in the woodpecker finch (Cactospiza pallida). This species is known to habitually use twigs or cactus spines to extract arthropods out of tree holes. We observed an adult and a juvenile bird using several barbed twigs from introduced blackberry bushes (Rubus niveus) which the adult bird had first modified by removing leaves and side twigs. The barbs of blackberry tools provide a novel functional feature not present in tools made from native plants and de-leafing of twigs never has been observed before. Both birds were observed using several of these tools to extract prey from under the bark of the native scalesia tree (Scalesia penduculta). They oriented the twigs such that the barbs pointed towards themselves; this rendered the barbs functional as they could be used to drag prey out of a crevice. The juvenile bird first watched the adult using the tool and then used the tool that the adult bird had left under the bark at the same location and in the same way as the adult. Our observation highlights the fact that opportunities for the transmission of social information do occur in the wild and indicates that woodpecker finches are flexible in their choice of tool material and tool modification.

Sometimes tool use is not the key: no evidence for cognitive adaptive specializations in tool-using woodpecker finches

The use and manufacture of tools has been considered to be cognitively demanding and thus a possible evolutionary driving factor of intelligence. Animal tool use provides the opportunity to investigate whether the use of tools evolved in conjunction with enhanced physical cognitive abilities. However, success in physical tasks may simply reflect enhanced general learning abilities and not cognitive adaptations to tool use. To distinguish between these possibilities, we compared general learning and physical cognitive abilities between the tool-using woodpecker finch, Cactospiza pallida , and its close relative, the small tree finch, Camarhynchus parvulus . Since not all woodpecker finches use tools, we also compared tool-using and nontool-using individuals, predicting that domain-specific experience should lead tool-using woodpecker finches to outperform nontool-users in a task that is similar to their natural tool use. Contrary to our predictions, woodpecker finches did not outperform small tree finches in either of the physical tasks and excelled in only one of the general learning tasks, and tool-using woodpecker finches did not outperform nontool-using woodpecker finches in the physical task closely resembling tool use. Our results provide no evidence that tool use in woodpecker finches has evolved in conjunction with enhanced physical cognition or that domain-specific experience hones domain-specific skills. This is an important contribution to a growing body of evidence indicating that animal tool use, even that which seems complex, does not necessitate specialized cognitive adaptations. ► Tool use may have evolved with enhanced cognitive abilities. ► Woodpecker finches did not outperform their nontool-using relatives in physical tasks. ► Nontool-using small tree finches made fewer errors and needed fewer trials in these tasks. ► Woodpecker finches were only better in an operant task that required perseverance. ► No indication that tool use evolved with enhanced cognitive abilities in this species.

Physical cognition and tool-use: performance of Darwin’s finches in the two-trap tube task

The trap tube is a classic test of causal reasoning abilities in animals in the physical domain. Recently, a modified version of this task improved its diagnostic capacity and allowed testing of non-tool-using animals. We used this modified two-trap tube task to compare the cognition of two Darwin's finch species: the woodpecker finch, Cactospiza pallida, a tool-using species, and the small tree finch, Camarhynchus parvulus, a closely related non-tool-using species. Not all woodpecker finches use tools in nature, and we therefore also tested non-tool-using individuals to assess the effect of experience on trap tube performance. No small tree finches and only two non-tool-using woodpecker finches solved the initial task which was operated using a pre-inserted piston. One tool-using woodpecker finch solved the task when allowed to use its own tool instead of the pre-inserted piston. The fact that none of these subjects transferred their knowledge when the features of the task changed, suggests that in this species, neither experience using tools nor the genetic composition of a tool-user are associated with the general physical cognitive skills required to solve the trap tube task.

Darwin's Finches as Seed Predators and Dispersers

We investigated seed predation and dispersal by nine Darwin's finch (Geospizinae) species, including species previously regarded as seed predators or insectivores. All nine ate fruit. Eight commonly discarded seeds, acting as short-distance dispersers. Seven defecated viable seeds, being therefore potential longer-distance dispersers. Fruit comprised the majority of dietary items in all four Geospiza species and Small Tree Finch (Camarhynchus parvulus). All except Common Cactus Finch (G. scandens) defecated intact seeds. The highest proportions of feces containing viable seeds were of Small Ground Finch (G. fuliginosa) and the “insectivorous” species Woodpecker Finch (Camarhynchus pallidus) and Warbler Finch (Certhidea olivacea). These two may be more important endochorous dispersers than other species that eat more fruit but are better seed predators. Intact seeds were found in 23% of fecal samples; 50% of the samples with intact seeds had viable seeds. The most frequently encountered intact seeds were of the tiny-seeded, fleshy-fruited Miconia robinsoniana and a sedge, Kyllinga brevifolia. Dry fruit, such as sedges and grasses, were usually crushed but occasionally found intact in feces, and might frequently be dispersed long distances. Seeds of larger-seeded, fleshy-fruited species were often discarded, but may be commonly dispersed short distances. Dispersal of plants by finches is probably more common than suggested by their predominant feeding patterns of seed predation and insectivory, and rare long-distance dispersal could be important for plant evolution and spread of introduced plants in the Galapagos Islands.

Interannual and interspecific variation in intensity of the parasitic fly, Philornis downsi, in Darwin’s finches

An integrative approach to managing host–parasite interactions that threaten species communities will benefit from identifying variation in parasite impact across host species, and host–parasite responses to annual climatic variation. We examine interannual, inter- and intraspecific variation in Philornis downsi intensity – an introduced blood sucking fly that causes high fitness costs in Darwin’s finches on the Galápagos Islands. We sampled 131 nests of six finch species (with nestling survival ⩾6 days post-hatching) between 1998 and 2005 on Santa Cruz Island. P. downsi total (per nest) and mean (per nestling) intensity differed across species and years. The woodpecker finch ( Cactospiza pallida), and the large tree finch ( Camarhynchus psittacula) had the highest total parasite intensity. Both species had comparatively large adult body mass, and we found a positive association between adult body mass and total parasite intensity among nestlings. P. downsi total and mean intensity was highest during the El Niño year of 1998. Surprisingly, despite a threefold difference in rainfall across lowland and highland habitats in other than the El Niño year, there was no difference in parasite intensity per nest between habitats. However, species composition of hosts and intraspecific brood size vary across habitats. Highland nests with larger broods and lower mean (per nestling) parasite intensity had higher fledging success. There was no significant effect of total parasite intensity on fledging success for intraspecific analyses. The percentage of nests with nestling mortality in each habitat ranged between 40% and 100% for all six host species.

Goliath Heron Fishing with an Artificial Bait?

Documentation of tool use by animals covers an array of species and tools, from chimpanzees (Pan troglodytes) making sponges to collect drinking water to Woodpecker Finches (Cactospiza pallida) using cactus spines to extract grubs (Beck 1980). One form of proto-tool use, placing bait such as bread to attract small fish within striking range, has been reported from seven bird species representing five orders. These include Pied Kingfisher (Ceryle rudis), Sunbittern (Eurypga helias), Lesser Black-backed Gull (Larus fuscus), Black Kite (Milvus migrans), plus three Ardeids: Green-backed Heron (Butorides striatus), Squacco Heron (Ardeola ralloides), and Black-crowned Night Heron (Nyticorax nyticorax) (Lefebvre et al. 2002; Riehl 2001). Only one of these species, the Green-backed Heron, has been observed using artificial lures such as twigs, feathers, and bits of plastic (Higuchi 1986). In this paper we report an observation of a Goliath Heron (Ardea goliath) apparently using a small stick as a lure to attract fish.

Cognitive abilities related to tool use in the woodpecker finch, Cactospiza pallida

Woodpecker finches are famous for their spontaneous tool use behaviour in the wild. They use twigs or cactus spines to pry arthropods out of crevices and use this ability more than any other tool-using species known. We experimentally investigated the cognitive abilities related to tool use. We chose three experimental designs that have been used to test several primate species (trap tube task and modification task) and New Caledonian crows (tool length task). One of six woodpecker finches was able to solve the trap tube task, and several individuals modified tools and chose twigs of appropriate length. Most subjects mastered these new tasks quickly, but we found no evidence that they were able to assess the problems in advance. These findings resemble those obtained for primates in these tasks.

FEEDING BEHAVIOR OF FOUR ARBOREAL DARWIN'S FINCHES: ADAPTATIONS TO SPATIAL AND SEASONAL VARIABILITY

Abstract In the Galapagos Islands climate and food abundance vary strongly among vegetation zones and between seasons. We studied the foraging behavior of four mainly insectivorous Darwin's finch species on Santa Cruz Island. We compared foraging behavior between (1) the arid zone, where food is scarce, with the humid Scalesia zone, where food is abundant; and (2) within each zone between dry and wet seasons. The four species used different feeding substrates in the two vegetation zones and reacted flexibly to the seasonal variation by changing feeding techniques and substrates. Species mainly specialized in resource use and feeding techniques or showed no change in niche breadth when food became more limited in dry conditions. In the arid zone during the dry season, the Large Tree Finch (Camarhynchus psittacula) relied on its powerful biting beak to bite open the bark of dry twigs. The Woodpecker Finch (Cactospiza pallida) used twigs and cactus spines to access arthropods in tree holes and was the only s...

The ecology of tool‐use in the woodpecker finch (Cactospiza pallida)

AbstractInsects, mammals and birds are known to use tools, but empirical evidence of the ecological importance of tool‐use is scarce. Here, we present the first ecological study of tool‐use by a bird species. Woodpecker finches use twigs or cactus spines to pry arthropods out of tree‐holes. We compared tool‐use during wet and dry seasons in two different vegetation zones: the Arid Zone and the humid Scalesia Zone. In the Scalesia Zone, where food was abundant and easily accessible, woodpecker finches rarely used tools. In contrast, in the Arid Zone, where food was limited and hard to access, they obtained half of their prey using tools during the dry season. Tool‐use enabled the birds to reach particularly large and otherwise inaccessible prey hidden in tree‐holes. Our data suggest that tool‐use in the woodpecker finch has evolved in response to the dry and unpredictable conditions in the coastal zone of the Galápagos Islands.

A New Perspective on The Evolutionary History of Darwin's Finches

The 13 species of finches found on the Galapagos Islands, and the one species from Cocos Island, together collectively known as Darwin's finches, are one of the better-studied groups of birds. Much has been learned about their ecology, behavior, and the short-term effects of natural selection (Lack 1947, Bowman 1961, Grant 1999). The four species of tree finch (Camarhynchus), six species of ground finch (Geospiza), the tool-using Woodpecker Finch (Cactospiza pallida), the Vegetarian Finch (Platyspiza crassirostris), the Warbler Finch (Certhidea olivacea), and the finch on Cocos Island (Pinaroloxias inornata) appear to fill different ecological roles via differentiation of bill size and shape (Grant and Grant 2002). In fact, most authors consider Darwin's finches to be a classic example of an adaptive radiation, owing to the great diversity in bill form and ecological habit that presumably evolved in a relatively short time. For example, Petren et al. (1999:321) noted, Species in this group show adaptive variation in beak size, beak shape and body size that is more typical of differences among [taxonomic] families of birds... (boldface added). Taxonomic History.-Darwin originally collected the finches from the Galapagos, not realizing what an evolutionary gold mine they would become (Sulloway 1982). In fact, he was not careful about labeling specimens as to the island from which a specimen was obtained, thus obscuring taxonomic boundaries. Subsequent work with better-labeled specimens revealed taxonomically significant patterns of variation. Gould (1837) recognized that different species existed in the collections from the Darwin expedition. However, Gould was unable to produce a stable classification. Since Gould's time, many of the major figures in avian taxonomy have published differing classifications. The succession of revisionary efforts attests to the difficult nature of classifying phenotypic variation among the finches. Although the species show considerable morphological diversity, many in fact are notoriously difficult to identify in the field (especially females and immatures). Populations from different species and islands overlap in morphometric space (Grant 1981).

Do woodpecker finches acquire tool-use by social learning?

Tool-use is widespread among animals, but except in primates the development of this behaviour is poorly known. Here, we report on the first experimental study to our knowledge of the mechanisms underlying the acquisition of tool-use in a bird species. The woodpecker finch Cactospiza pallida, endemic to the Galápagos Islands, is a famous textbook example of tool-use in animals. This species uses modified twigs or cactus spines to pry arthropods out of tree holes. Using nestlings and adult birds from the field, we tested experimentally whether woodpecker finches learn tool-use socially. We show that social learning is not essential for the development of tool-use: all juveniles developed tool-use regardless of whether or not they had a tool-using model. However, we found that not all adult woodpecker finches used tools in our experiments. These non-tool-using individuals also did not learn this task by observing tool-using conspecifics. Our results suggest that tool-use behaviour depends on a very specific learning disposition that involves trial-and-error learning during a sensitive phase early in ontogeny.

A phylogenetic reanalysis of allozyme variation among populations of Galapagos finches

We reanalysed Yang & Pattern's allozyme data, published in Auk in 1981, of Darwin's finches with a variety of distance and cladistic methods to estimate the phylogeny of the group. Different methods yielded different results, nevertheless there was widespread agreement among the distance methods on several groupings. First, the two species of Camarhynchus grouped near one another, but not always as a monophyletic group. Second, Cactospiza pallida and Platyspiza crassirostris formed a monophyletic group. Finally, all the methods (including parsimony) supported the monophyly of the ground finches. The three distance methods also found close relationships generally between each of two populations of Geospiza scandens, G. difficilis and G. conirostris. There is evidence for inconstancy of evolutionary rates among species. Results from distance methods allowing for rate variation among lineages suggest three conclusions which differ from Yang and Patton's findings. First, the monophyletic ground finches arose from the paraphyletic tree finches. Yang and Patton found that the ground finches and tree finches were sister monophyletic taxa. Second, Geospiza scandens appears to be a recently derived species, and not the most basal ground finch. Third, G. fuliginosa is not a recently derived species of ground finch, but was derived from an older split from the remaining ground finches. Most of these conclusions should be considered tentative both because the parsimony trees disagreed sharply with the distance trees and because no clades were strongly supported by the results of bootstrapping and statistical tests of alternative hypotheses. Absence of strong support for clades was probably due to insufficient data. Future phylogenetic studies, preferably using DNA sequence data from several unlinked loci, should sample several populations of each species, and should attempt to assess the importance of hybridization in species phylogeny.

Tool Use by Bristle-Thighed Curlews Feeding on Albatross Eggs

In strictest sense, tool use is the use of an external object as a functional extension of mouth or beak, hand or claw, in attainment of an immediate goal (van Lawick-Goodall 1970). Tool use by birds has been reported for a number of species but is considered uncommon (Morse 1968, van Lawick-Goodall 1970). Examples include Woodpecker Finches (Cactospiza pallida) and Green Jays (Cyanocorax yncas) probing for insects with twigs (Lack 1947, Gayou 1982), Blackbreasted Kites (Hamirostra melanosternon) and Egyptian Vultures (Neophron percnopterus) dropping stones onto ratite eggs (Chisholm 1954, van Lawick-Goodall and van Lawick-Goodall 1966), and a Fan-tailed Raven (Corvus rhipidurus) striking a ping-pong ball with a rock (presumably mistaking ball for an egg; Andersson 1989). Here, we report five cases of tool use by Bristlethighed Curlews (Numenius tahitiensis) feeding on albatross eggs and suggest that tool use is an extension of behavior commonly employed by foraging Bristle-thighed Curlews. To our knowledge, tool use has not been reported previously for any shorebird. Bristle-thighed Curlews breed in western Alaska and winter on islands in central and south Pacific (AOU 1983). We observed curlews on Tern Island (2345'N, 16610'W) and Laysan Island (25?46'N, 171?44'W) in Northwestern Hawaiian Islands, which extend for 2,000 km WNW of main Hawaiian Islands and comprise northern limit for wintering Bristle-thighed Curlews. The natural history of Tern Island and Laysan Island is described by Amerson (1971) and Ely and Clapp (1973), respectively. In Northwestern Hawaiian Islands, Bristlethighed Curlews forage in terrestrial habitats, feeding primarily on spiders, land crabs, and a wide variety of insects (J. S. Marks and R. L. Redmond, unpubl. data). Food items too large to be swallowed whole often are slammed against ground until they are broken (J. S. Marks, pers. observ.). In a typical slamming event, curlew holds food item in tip of its bill, raises it overhead, and then vigorously slams it against ground. This sequence is repeated until food item is broken into pieces. Usually, curlew slams food item against a flat rock. On Laysan and Tern islands, most commonly slammed items are ghost crabs (Ocypode laevis and O. ceratophthalma). Flightless chicks on breeding grounds slam nonfood items such as lichen, moss, and plastic flagging (R. E. Gill, pers. comm.), and hatching-year curlews newly arrived on Laysan often slam seabird feathers, old crab shells, and seaweed. Adult curlews confine slamming behavior to food items and in Alaska have never been observed to slam food during brood-rearing period (R. E. Gill and B. J. McCaffery, pers. comm.). Therefore, slamming behavior is probably innate. Between 2 and 10 January 1991, Hall observed four cases (involving two banded adults and at least one unbanded bird of unknown age) of tool use by curlews feeding on abandoned eggs of Black-footed (Diomedea nigripes) or Laysan (D. immutabilis) albatrosses on Tern Island. In each case, curlew picked up a small piece of coral (<2 cm diameter) and threw it at egg repeatedly, breaking a hole in shell (Fig. 1). The curlew then inserted its bill into hole, enlarged opening, and fed upon Marks saw an unbanded adult curlew use same behavior to open a Black-footed Albatross egg on Laysan Island on 13 February 1991. Except for substitution of a stone for a food item, use of stones to open eggs is identical to slamming behavior and very likely is derived from it. Tool use by Bristle-thighed Curlews is similar to that by Egyptian Vultures in that stones are thrown forcefully at eggs rather than dropped onto them (van LawickGoodall and van Lawick-Goodall 1966). Bristle-thighed Curlews are well-known predators of seabird eggs (Bailey 1956, Ely and Clapp 1973). On Laysan Island and Tern Island, curlews break smaller eggs (e.g., shearwater, petrel, and tern eggs) by pecking them with their bills or by slamming or dropping them on ground. Bailey (1956) reported that Bristlethighed Curlews eating albatross eggs would tap eggs with their curved beaks and drain contents. In hundreds of hours of observation, we never saw a curlew open an intact albatross egg with its bill. We have seen curlews pecking at albatross eggs that have been opened by Ruddy Turnstones (Arenaria interpres), however, and it is possible that turnstones initially opened eggs that Bailey observed. Bristle-thighed Curlews often feed by probing, and Received 20 April 1992. Accepted 10 July 1992.

Four New Species of Isospora from the Small Tree Finch (Camarhynchus parvulus) from the Galapagos Islands1

Four isosporan species are described from the small tree finch, Camarhynchus parvulus from Isabela Island on the Galapagos Archipelago. Isospora exigua n. sp. oocysts subspheroidal, one-layered, smooth, yellow-brown color, 20.4 X 20.1 (20-23 X 18-23) microns, with no micropyle, residuum, or polar body. Sporocysts ovoidal, 14 X 9.5 (13-15 X 8-10) microns, with small Stieda and substieda bodies and irregular-shaped residuum. Isospora rotunda n. sp. oocysts subspheroidal, single-layered, smooth, yellow-brown wall with large polar body and no micropyle or residuum, 20.9 X 20.8 (20-24 X 19-23) microns. Sporocysts ovoidal, 15 X 9.7 (13-16 X 9-10) microns with knob-like Stieda bodies, prominent substieda bodies and round residuum. Isospora fragmenta n. sp. oocysts subspheroidal with no micropyle or residuum but with many splinter-like polar granules and a smooth, colorless, single-layered wall, 25.3 X 24.2 (24-27 X 23-25) microns. Sporocysts piriform 15.4 X 11.5 (14-17 X 11-12) microns with knob-like Stieda bodies, prominent substieda bodies, and irregular-shaped residuum. Isospora temeraria n. sp. oocysts ellipsoidal with one polar body, no micropyle or residuum, and wall of a single layer, smooth, yellow-brown color, 25.4 X 21.1 (21-30 X 17-23) microns. Sporocysts piriform, 15 X 10 (14-15 X 9-11) microns with knob-like Stieda bodies, prominent substieda bodies, and a round residuum. One woodpecker finch, Cactospiza pallida, was found to be infected with I. exigua, and a warbler finch, Certhidea olivacea was infected with I. fragmenta.