Behavioral responses of maned wolves (Chrysocyon brachyurus, Canidae) to different categories of environmental enrichment stimuli and their implications for successful reintroduction

The maned wolf (Chrysocyon brachyurus, Illiger, 1815, Canidae) is a threatened species that inhabits the cerrados of Brazil, Argentina, Peru, Bolivia, Paraguay, and Uruguay. Captive maned wolves could be potentially used in reintroduction programs for species conservation; however, it is necessary that their behavior and cognitive abilities are conserved. Environmental enrichment is a tool used to stimulate captive animals and maintain a natural behavioral repertoire. To compare the variation of captive maned wolves' behavioral responses to environmental enrichment, we studied three maned wolves held by Belo Horizonte Zoo, Brazil. Foraging, interspecific, and intraspecific stimuli were offered to the animals and their responses were compared with a baseline and postenrichment treatments. The test was used to help in choosing which one of the three individuals would participate in a reintroduction project. The results showed that stimuli type did influence the animal's responses, and that individually wolves responded differently to foraging, interspecific, and intraspecific enrichment items (P80.05 for some behaviors in each enrichment category). The individual's personality seemed to influence their behavioral responses, with animals showing bold and shy responses, and this trait should be considered during decision makings for reintroduction.     

Behavioral and hormonal responses to the availability of forage material in Western lowland gorillas (Gorilla gorilla gorilla)

We investigated how forage material affects indicators of welfare in three male Western lowland gorillas (Gorilla gorilla gorilla) at the Detroit Zoo. In addition to their maintenance diet and enrichment foods, the gorillas generally received forage material four times a week. From this baseline, we systematically manipulated how much forage material the group received on a weekly basis, with either daily or bi (twice)‐weekly presentation of browse (mulberry, Morus sp.) or alfalfa hay. We collected behavioral data (60 hr per gorilla) and measured fecal glucocorticoid metabolites (FGM). Mixed models indicated that the presence of forage material significantly increased time feeding (F_2,351 = 9.58, p < 0.001), and decreased rates of noncontact aggression (F_2,351 = 3.69, p = 0.03), and regurgitation and reingestion (F_2,353 = 4.70, p = 0.01). Regurgitation and reingestion were never observed during the condition when forage material was provided daily. When forage material was provided, time spent feeding was similar across gorillas, compared to a disproportionately greater amount of time spent feeding by the dominant individual when forage material was absent. Providing forage material in addition to the regular diet likely created more opportunities for equitable feeding for the subordinate gorillas. FGM concentrations did not vary based on the presence or type of forage material available and, instead, likely reflected group social dynamics. In general, alfalfa and mulberry had similar impacts on behavior, indicating that alfalfa can be an adequate behavioral substitute during times when browse is less readily available for gorillas housed in seasonally variable climates.     

Predation risk and resource abundance mediate foraging behaviour and intraspecific resource partitioning among consumers in dominance hierarchies

Dominance hierarchies and the resulting unequal resource partitioning among individuals are key mechanisms of population regulation. The strength of dominance hierarchies can be influenced by size‐dependent tradeoffs between foraging and predator avoidance whereby competitively inferior subdominants can access a larger proportion of limiting resources by accepting higher predation risk. Foraging‐predation risk tradeoffs also depend on resource abundance. Yet, few studies have manipulated predation risk and resource abundance simultaneously; consequently, their joint effect on resource partitioning within dominance hierarchies are not well understood. We addressed this gap by measuring behavioural responses of masu salmon Oncorhynchus masou ishikawae to experimental manipulations of predation risk and resource abundance in a natural temperate forest stream. Responses to predation risk depended on body size and social status such that larger fish (often social dominants) exhibited more risk‐averse behaviour (e.g. lower foraging and appearance rates) than smaller subdominants after exposure to a simulated predator. The magnitude of this effect was lower when resources were elevated, indicating that dominant fish accepted a higher predation risk to forage on abundant resources. However, the influence of resource abundance did not extend to the population level, where predation risk altered the distribution of foraging attempts (a proxy for energy intake) from being skewed towards large individuals to being skewed towards small individuals after predator exposure. Our results imply that size‐dependent foraging–predation risk tradeoffs can weaken the strength of dominance hierarchies by allowing competitively inferior subdominants to access resources that would otherwise be monopolized.     

New insights into the physiology of natural foraging

The purpose of this symposium was to examine how foraging physiology is studied in the field across a diversity of species and habitats. While field studies are constrained by the relatively poor ability to control the experiment, the natural variability in both the environment and animal behavior provides insights into adaptation to change that are usually not tested in the laboratory. Talks in this session examined how foraging energy (both costs and gains) is partitioned over time. "Time," in this case, ranged from evolutionary time (how different animals are designed to most efficiently forage), to long, lifetime periods (development of foraging ability and growth), to short-duration feeding bouts, and ultimately to the minutes to hours following ingestion (metabolic and biochemical changes). From this diversity, two core themes emerged: that foraging strategies and behaviors are limited by physiology and biochemical processes and that time plays a central role in the organization of foraging behaviors and the physiological processes that underlie those behaviors.     

Fitness consequences of cooperative colony founding in the desert leaf-cutter ant Acromyrmex versicolor

The evolution of cooperative colony foundation (pleometrosis)in ants has been attributed to conversion of extra resourcesinto increased competitive ability. Most cooperative foundingspecies provide these additional resources from internal fatstores; however, in those species that forage for resources, theextent and type of individual investment in multiqueen coloniesis not well understood. We compared singly- and group-foundedlaboratory colonies of the desert leaf-cutter ant Acromyrmexversicolor to investigate how cooperation affects colony survival,foraging success, and worker production. Under laboratory conditions,single foundresses were significantly less likely to initiatea successful symbiotic fungus garden, which inevitably led to colonystarvation and death. If gardens were initiated successfully,however, there was no difference in the growth trajectoriesand foraging patterns between colony types. Cooperation in thisspecies may more likely be maintained by survival benefits thanby growth rate differences, which may be constrained in groupsby individual and colony-level costs.     

An exploration of the relationship between recruitment communication and foraging in stingless bees

Social information is widely used in the animal kingdom and can be highly adaptive. In social insects, foragers can use social information to find food, avoid danger, or choose a new nest site. Copying others allows individuals to obtain information without having to sample the environment. When foragers communicate information they will often only advertise high-quality food sources, thereby filtering out less adaptive information. Stingless bees, a large pantropical group of highly eusocial bees, face intense inter- and intra-specific competition for limited resources, yet display disparate foraging strategies. Within the same environment there are species that communicate the location of food resources to nest-mates and species that do not. Our current understanding of why some species communicate foraging sites while others do not is limited. Studying freely foraging colonies of several co-existing stingless bee species in Brazil, we investigated if recruitment to specific food locations is linked to 1) the sugar content of forage, 2) the duration of foraging trips, and 3) the variation in activity of a colony from 1 day to another and the variation in activity in a species over a day. We found that, contrary to our expectations, species with recruitment communication did not return with higher quality forage than species that do not recruit nestmates. Furthermore, foragers from recruiting species did not have shorter foraging trip durations than those from weakly recruiting species. Given the intense inter- and intraspecific competition for resources in these environments, it may be that recruiting species favor food resources that can be monopolized by the colony rather than food sources that offer high-quality rewards.     

An investigation of browsing enrichment,especially non-leaf foraging,on giraffes (Giraffa camelopardalis reticulata) at Kyoto City Zoo in Japan

Browsing enrichment may aid in developing species-specific behaviors for giraffes managed in zoos as a means of improving animal welfare. By nature, giraffes are tree-feeding animals, including tree bark, but the extent of food other than leaves as a form of browsing enrichment has not been well investigated. Therefore, to investigate the effectiveness of non-leaf foraging, three giraffes at the Kyoto City Zoo in Japan were observed for 228 h from May 2019 to February 2020. In conjunction with behavioral instantaneous sampling, tree use (landscape tree or enrichment branch) and plant part (leaves, twigs, or barks) were recorded by the 1-0 sampling method. There was no significant change in the foraging behavior on the leaves of enriched branches, nor was there any significant change in the foraging behavior of the giraffes, except for one animal in the deciduous phase. No significant changes were observed in rumination or other behaviors between the two phases. Although vegetation foraging behavior significantly decreased, except for one animal, dry hay foraging behavior significantly increased in all the animals during the deciduous phase. Some individuals also showed a significant increase in the foraging behavior for non-leafy parts of the enrichment branches (twigs and bark) during the deciduous phase. This suggests that in some tree species, giraffes forage on the bark and twigs to compensate for the loss of leaves during the deciduous phase, similar to feeding on hay or hay cubes as a substitute for tree leaves.     

Optimal foraging and the traveling salesman

Optimal foraging models are examined that assume animals forage for discrete point resources on a plane and attempt to minimize their travel distance between resources. This problem is similar to the well-known traveling salesman problem: A salesman must choose the shortest path from his home office to all cities on his itinerary and back to his home office again. The traveling salesman problem is in a class of enigmatic problems, called NP-complete, which can be so difficult to solve that animals might be incapable of finding the best solution. Two major results of this analysis are: (1) The simple foraging strategy of always moving to the closest resource site does surprisingly well. More sophisticated strategies of “looking ahead” a small number of steps, choosing the shortest path, then taking a step, do worse if all the resource sites are visited, but do slightly better (less than 10%) if not all the resource sites are visited. (2) Short cyclical foraging routes resulted when resources were allowed to renew. This is suggested as an alternative explanation for “trap-lining” in animals that forage for discrete, widely separated resources.     

Effects of sward structure on herbivore foraging behaviour in a South African savanna: An investigation of the forage maturation hypothesis

Abstract: The grass layer of savannas is characterized by strong temporal and spatial heterogeneity in the quantity and quality of forage. Besides this, there is strong variation in other aspects of sward structure, here defined as sward chemistry, morphology, architecture and species composition. The forage maturation hypothesis (FMH) is based on the temporal dynamics of forage quantity and quality of grasslands. Recently this hypothesis has been used to explain the foraging behaviour of large herbivores as an optimal solution for balancing forage ingestion and forage digestion, leading to a maximization of daily rates of forage intake in patches of intermediate forage quantity. However, so far studies using this hypothesis have been constrained to mono‐specific forage resources or have ignored inter‐patch variation in sward structure. We studied the foraging behaviour of cattle in a South African savanna. We explicitly addressed forage quantity and quality, and the structure of seven sward types in order to investigate (i) their effects on foraging behaviour; and (ii) the assumptions and predictions of the FMH for foraging behaviour in grasslands with pronounced variation in sward structure. The results indicated that the assumptions of the FMH were met and that forage quantity affected forage intake the most, with sward structure having little or no effect. The predicted maximum rate of daily forage intake agreed with the results of previous studies. However, the forage quantity at which this maximum intake rate was found, was larger than expected based on the results of some studies. It is likely that this discrepancy resulted from the use of artificial leaf‐only grass swards in these studies. The results suggest that the FMH can be used to explain the foraging behaviour of herbivores over a wide range of sward structures.     

The Effect of Social Hierarchy on Captive Coyote (Canis latrans) Foraging Behavior

Foraging efficiency of individuals in pack forming species may be influenced by social dynamics within a pack. The effects of social hierarchy in particular may influence individual foraging behavior in canids, such as coyotes (Canis latrans). To examine the impact of social hierarchy on foraging behavior, we tested 16 captive coyotes in eight naturally established dominant–subordinate pairs, using the guesser–knower paradigm. We measured the efficiency of subordinate coyotes to relocate a food resource when alone and then allowed pairs to forage together, such that subordinates had prior knowledge of food location but dominants did not. To determine whether (1) subordinates used a direct or discursive strategy to obtain food in the presence of a dominant and (2) dominants used an exploitative or independent strategy to obtain food in the presence of a subordinate with previous knowledge, we measured their search efficiency (e.g., correct choice of area, feeder, and latency to correct feeder). Results showed subordinates learned to relocate food and increase efficiency when alone. In a social context, however, subordinate efficiency decreased. That is, subordinates approached the correct area, but searched more feeders before finding the correct one. Dominants initially used an independent search strategy but then quickly displaced the subordinate and monopolized the resource, reducing subordinate efficiency further. Despite continual displacement and reduction in efficiency, subordinates did not alter their foraging strategy over time. Our results suggest prior information can improve individual foraging advantage, but that social status strongly impacts individual foraging efficiency in social species such as coyotes.     

Long-Term Habitat Use by Mountain Gorillas (Gorilla gorilla beringei). 2. Reuse of Foraging Areas in Relation to Resource Abundance, Quality, and Depletion

Resource depression caused by current feeding and the rate of resource renewal should influence foragers' decisions about when to revisit foraging areas. Adjustment of foraging paths and revisit rates should be particularly important when resources renew slowly. Foragers can also benefit by returning more often to highly profitable than to less profitable foraging areas. Many highly frugivorous primates seem to time revisits to fruit sources so as to harvest fruit efficiently and, also, use efficient search paths. Fewer data on non-frugivores exist. Mountain gorillas are folivores that eat mostly perennially available, continuously growing herbs and vines. Vegetation regenerates slowly from the effects of gorilla trampling, though trampling can also facilitate food species productivity, at least in the short term. Adjustment of intervals between visits to foraging areas to the extent of previous use and to resource renewal rates should increase gorilla foraging efficiency. Long-term data on habitat use by 6 mountain gorilla social units show that revisit intervals vary in association with variation in the extent of previous use and in plant productivity. However, they also revisit areas more often, the higher the biomass and nutritional quality of food there. These data are generally consistent with the hypothesis that the gorillas crop resources on a sustained-yield basis, though more precise data on areal revisits and complementary long-term data on vegetation composition would be needed to test the hypothesis.     

Territorial Dominance of Male Laboratory Mice

Social interaction and spatial distribution among male mice (Mus musculus) were observed. The enclosure was divided into three compartments, left, right and center. Each side compartment contained two males for 3 d and then the doors that led to the center compartment were opened for 7 d. The dominant male was removed 3 d after the opening day. The results indicate that the dominant male monopolized its own territory including the compartment where it had dwelt before opening the doors. The other subordinates huddled together in the opposite compartment. The dominant male patrolled more frequendy than subordinates and sometimes attacked subordinates. One of the subordinates rapidly became dominant after the removal of the dominant male. The secondary dominant male monopolized the familiar area and attacked subordinates, as the dominant male had done.     

Influence of stock density and rate and temporal patterns of forage allocation on the diet mixing behavior of sheep grazing sagebrush steppe

An animal's ability to select a diet depends on forage availability, the density of herbivores, and the allocation of forage resources. We hypothesized that the temporal and spatial availability of forages in sagebrush steppe vegetation both influence food selection and may encourage lambs to learn to use sagebrush, a shrub that contains high levels of terpenes that limit food intake. We conducted a field study with three treatments of 20 lambs each. Forage resources were manipulated by restricting grazing areas. Lambs in treatment H grazed at a high stock density, whereas lambs in treatment L grazed at a low stock density; both groups were moved to fresh pasture daily. Lambs in treatment H3 had three times the area of treatment H, but they were moved every 3 days, making the total area grazed by H and H3 equal, but with a different temporal allocation of forage. Scan sampling was used to record the incidence of consumption among sagebrush and understory herbs. During 24 days of conditioning, stock density and temporal patterns of forage allocation both influenced the behavior of lambs. Lambs in H spent more time foraging on sagebrush (25%) than lambs in H3 (16%), and lambs in both H and H3 spent more time foraging on sagebrush than lambs in L (1%) (P < 0.05). For lambs in H3, foraging on sagebrush was cyclic and depended on the daily availability of herbs. Use of sagebrush, expressed as a percentage of total foraging time, was <1% for day 1, 13% for day 2, and 37% for day 3 (P < 0.0001). Importantly, use of sagebrush by H3 and H increased steadily as the trial progressed, whereas use of sagebrush by L was consistently low (P < 0.05). Following conditioning, when lambs were tested at low stock densities during preference test 1, use of sagebrush did not differ by groups, but at higher stock densities in preference test 2, their use of sagebrush varied by treatments: H > H3 > L (P < 0.005). Thus, the availability of alternative foods, manipulated through animal density and the temporal allocation of those resources, both affected how readily lambs learned to use sagebrush.     

Foraging efficiency and the fitness consequences of spatial marking by ladybeetle larvae

Marking and avoiding poor‐quality resources can be an important mechanism by which animals lacking a spatial memory can maximize their foraging efficiency. Here, we investigate the behaviour of larval Harmonia axyridis ladybeetles that leave chemical tracks as they forage. We built a model of an individual larva foraging for aphids, parameterized it using experimental data, and used the model to predict the effect of larval track production and detection on foraging efficiency, an important component of fitness. The model predicted that there is an optimal sensitivity of larvae to tracks which maximizes foraging efficiency; if the larva is too sensitive to tracks, it will avoid areas that might still contain resources, whereas if it is too insensitive, it will forage in areas that have depleted resources. Furthermore, the increased efficiency conferred by detecting tracks depends on the spatial arrangement of resources, with more aggregated resource distributions allowing greater benefits of detecting tracks. We tested the predictions of the model experimentally by measuring predation on aggregated versus dispersed soybean aphids by H. axyridis larvae whose ability to produce tracks was experimentally manipulated. The experiments corroborated the results of the model: larvae that could produce tracks consumed more aphids than those that could not, and this difference was greatest when aphids were aggregated among plants. Our results suggest that larval tracks play an important role in foraging efficiency, and we discuss implications for the evolution of larval track production and detection in ladybeetles.     

同域分布3种啄木鸟冬季取食的生态位差异

为了掌握黑啄木鸟、三趾啄木鸟和大斑啄木鸟的冬季取食行为特征,特别是三者之间取食生态位的差异,于2016年1月5-13日,在黑龙江省凉水国家级自然保护区以样线法结合样方法对3种啄木鸟的取食生境和取食行为进行了系统调查,收集了15个生境和行为特征变量数据。共布设45条样线,484个对照样方,收集312组啄木鸟取食数据,其中黑啄木鸟73组,三趾啄木鸟97组,大斑啄木鸟142组。多变量回归树和多分类逻辑斯谛分析结果显示,3种啄木鸟在所调查的15项特征上存在显著分异。采用基于利用-可利用方法的Bailey''s方法和双因子方差分析,分别对3种啄木鸟的生境选择和行为特征进行分析,结果显示：黑啄木鸟和三趾啄木鸟偏好在郁闭度较高的原始云、冷杉林中取食,而大斑啄木鸟则随机地在各种林型、生境中取食。黑啄木鸟、三趾啄木鸟多在树干取食,黑啄木鸟更常在倒木上取食,而大斑啄木鸟则多在树冠层取食。黑啄木鸟基本只在主干上凿洞,其他两种特别是大斑啄木鸟则可以在侧枝上取食。与黑啄木鸟和大斑啄木鸟凿洞取食昆虫不同,三趾啄木鸟多通过扒去树皮获得食物。黑啄木鸟的取食树基本为死树,单树取食时间最长,大斑啄木鸟多在活树上取食,单树取食时间最短,经常更换取食树,而三趾啄木鸟的取食树则死活参半,单树取食时间也较长。黑啄木鸟的冬季取食行为节律表现为双峰形,日出后和日落前各有一个活动高峰,其他两种则于白天持续取食。3种啄木鸟取食生境和行为生态位的差异,使它们能够更有效地利用有限的食物资源,共存于同一森林。     

Studies on "stiffness of extremities disease" in the yak (Bos mutus)

Wild yak (Bos mutus) are affected by a disorder known colloquially as "stiffness of extremities disease," characterized by emaciation, lameness, stiffness in the gait, enlargement of the costochondral junctions, and abnormal curvature in the long bones. Results from preliminary epidemiologic and clinical observations suggested that this was a local, nutritional and metabolic disease associated with some mineral deficiency. Our objective was to determine the possible relationship between this disease and phosphorus (P) deficiency. We found that P concentrations in forage samples from affected areas were significantly lower than were those from unaffected areas, and the mean calcium:P ratio in the affected forage was 14:1. Phosphorus concentrations of blood, bone, teeth, and hair from affected yak were also significantly lower than were those from reference yak. Serum P levels of affected animals were much lower than were those of reference yak, whereas serum alkaline phosphatase levels were significantly higher than were those from reference yak. The P deficiency disease could be cured with supplement of disodium hydrogen phosphate (Na(2)HPO(4)). We conclude that the disease is mainly caused by P deficiency in forage.     

Foraging strategies as a function of season and rank among wild female chimpanzees (Pan troglodytes)

Among mammals, female reproduction is generally thought to befood limited, and dominance should theoretically afford high-rankingfemales with access to better food resources. Although the importanceof dominance rank among female chimpanzees (Pan troglodytes)has been debated in the past, mounting evidence suggests thatrank is very important among females (P. t. schweinfurthii)at Gombe National Park, Tanzania. In this study, we investigatedthe influence of season and dominance rank on female foragingstrategies. We found that high-ranking females spent less timeforaging and tended to have a narrower diet breadth and higherdiet quality than subordinate females. In this way, subordinatefemale foraging strategies were consistent with how femalesin general adapted to periods of food scarcity. The resultsof this study therefore suggest that low-ranking females mayface persistent "food scarcity" as a result of interferencefood competition. We also provide evidence that subordinatesmay forage less efficiently because they occupy lower qualityhabitats or avoid associating with dominant females in sharedareas.     

不同品种(系)牧草镉修复能力综合评价

该研究选用3种高丹草、2种苏丹草、2种杂交狼尾草、一年生黑麦草和多年生黑麦草共9个牧草品系,采用盆栽试验,设置0(CK)、10(Cd10)、20 mg/kg(Cd20)镉胁迫处理,考察不同品系的生长指标、镉含量和富集指标,运用极差化法和主成分分析建立综合评价模型,通过计算各牧草在模型中的综合得分,筛选出最适宜实地修复的牧草,探究不同品种和不同品系牧草的镉修复能力差异,建立Cd污染土壤植物修复能力评价体系,发掘兼顾富集量和后处理的镉污染土壤植物修复资源。结果表明：(1)镉胁迫会不同程度降低牧草的株高和生物量,其中江苏苏丹草在Cd10和Cd20中的耐胁迫能力均较强;(2)在Cd10和Cd20处理下,一年生和多年生黑麦草均具有较高的地上部和地下部Cd含量,高丹草的3个品系在Cd含量和Cd积累量两方面存在较大差异;(3)在Cd10和Cd20处理下,高丹草和黑麦草的富集指标表现优异,且富集指标在高丹草品系间存在较大差异;(4)2个镉质量分数处理下综合评价得分最高的均是一年生黑麦草,其次为高丹草。研究表明,参试牧草对镉胁迫均有较强的耐受性,但耐受能力和富集能力在品系间存在明显差异,并以高丹草品系间差异最大;一年生黑麦草能耐受20 mg/kg以下镉胁迫,且生物量较小,对镉有较强的浓缩效应,可作为镉污染土壤实地修复的可靠材料;综合评价模型可作为镉污染修复植物资源筛选的可靠方法。     

Influence of Abiotic Factors and Floral Resource Availability on Daily Foraging Activity of Bees

In this study, the daily and seasonal influences of abiotic factors and the amount of floral resources on the foraging frequency of bees were determined. The experiments were performed, during 12 consecutive months, in the main floral sources used by bees in a secondary forest fragment. The foraging frequency of each bee species on flowers of each plant was recorded for 20-min periods, every hour. To verify whether the foraging activity is influenced by abiotic factors, Pearson’s correlation analysis and linear regression tests were performed for the dominant bee species. Temperature and luminosity were the two main abiotic factors regulating foraging activities of bees. A positive correlation was found between the foraging frequency of most bees and these two variables. Conversely, the foraging activity was influenced neither by the relative humidity nor by the wind speed. The activity of each species depends on a combination of factors that include not only abiotic variables, but also the amount of floral resources available during the day, body size, and behavior of each visitor. After a certain period of the day, the scarcity of floral resources produced by most plants can stimulate the bees to forage in the flowers early in subsequent days, which may occur before the period in which the abiotic conditions are really favorable.     

Linking foraging decisions to residential yard bird composition

Urban bird communities have higher densities but lower diversity compared with wildlands. However, recent studies show that residential urban yards with native plantings have higher native bird diversity compared with yards with exotic vegetation. Here we tested whether landscape designs also affect bird foraging behavior. We estimated foraging decisions by measuring the giving-up densities (GUD; amount of food resources remaining when the final forager quits foraging on an artificial food patch, i.e seed trays) in residential yards in Phoenix, AZ, USA. We assessed how two yard designs (mesic: lush, exotic vegetation; xeric: drought-tolerant and native vegetation) differed in foraging costs. Further, we developed a statistical model to calculate GUDs for every species visiting the seed tray. Birds foraging in mesic yards depleted seed trays to a lower level (i.e. had lower GUDs) compared to birds foraging in xeric yards. After accounting for bird densities, the lower GUDs in mesic yards appeared largely driven by invasive and synanthropic species. Furthermore, behavioral responses of individual species were affected by yard design. Species visiting trays in both yard designs had lower GUDs in mesic yards. Differences in resource abundance (i.e., alternative resources more abundant and of higher quality in xeric yards) contributed to our results, while predation costs associated with foraging did not. By enhancing the GUD, a common method for assessing the costs associated with foraging, our statistical model provided insights into how individual species and bird densities influenced the GUD. These differences we found in foraging behavior were indicative of differences in habitat quality, and thus our study lends additional support for native landscapes to help reverse the loss of urban bird diversity.