Mixed-species Flocks Research Articles

Great tits benefit from feeding in mixed-species flocks: a field experiment

Patch depletion, food intake and aggressive interactions were studied in flocks of great tits, Parus major, and in mixed-species flocks of great tits and marsh tits, P. palustris, exploiting one or two patches. Both male and female great tits had a higher feeding rate in mixed-species flocks than in single-species flocks. Food was depleted more quickly and aggression was lower in mixed flocks. The difference in intake rates between males and females was lower when they were feeding over two patches than on one patch because of the dispersion and consequent reduction in aggressive interactions in the group. Marsh tits and female great tits were more likely than male great tits to be attracted to a neighbouring food patch by another individual. Marsh tits outside the flock were a greater attraction to individuals from the group than were great tits. Individuals appeared to feed less efficiently in two patches as they spent longer there than in one patch of the same size and food density.

Foraging Behavior and Diet of the Helmeted Manakin

I studied the foraging behavior and diet of the Helmeted Manakin (Antilophia galeata) in the gallery forests in the cerrado (savanna) region of central Brazil. Observations of 21 color-marked birds were made from April 1988 to March 1989 on a 2.5-ha study plot in a gallery forest. They showed that Helmeted Manakins are highly frugivorous (85.7% of foraging observations were on fruits; all stomach contents analyzed had fruits while arthropods were present in only 24.5%; and 96.2% of the fecal masses collected under a nest had fruits while 6 1.5% had arthropods); and take fruit mostly (46.5% of the observations) while in flight (sallies). Helmeted Manakins ate fruits of 17 species of 12 families of plants, as well as arthropods such as Araneae, Orthoptera, Coleoptera, Diptera, and Hymenoptera. One to six Helmeted Manakins attended 63.6% of the mixed-species flocks observed. Green birds (females and immature males) foraged at lower heights (6.5 * 4.6 m) than adult and subadult males, which foraged at a height (8.2 f 4.4 m) closer to where they sang (10.2 + 3.8 m) or called (8.4 f 4.8 m). The Helmeted Manakin showed similarities to other manakins in the diet and foraging tactics used, even though it may not be promiscuous (Marini and Cavalcanti, in prep.) and has an unique geographical distribution among dichromatic manakins.

Larids, Scolopacids, and Passerines Exploiting Ephemeral Prey at Talan Island, Russia

We report an unusual multispecies foraging assemblage that included larids, shorebirds and passerines which exploited a highly concentrated and ephemeral prey source over a period of three days in July and August 1988. During studies of breeding biology, food-habits and host-parasite ecology among a diverse colonial avifauna at Talan Island in the northern Sea of Okhotsk (59018'N; 149002'E) we observed the formation of mixed-species flocks during extreme high tides of 31 July, 1 August, and 13 August 1988. The first assemblage involved a maximum of 60 birds, including about 45 black-legged kittiwakes (Rissa tridactyla) and 15 slaty-backed gulls (Larus schistisaugus). Feeding activity was intense within 1-3 m of the shore. All birds swam slowly while vigorously dipping and picking minuscule prey items from the surface of the water. The duration of foraging by this flock was not determined. As birds dispersed, we were able to collect numerous pupae and late instar larvae (3-7.3 mm in length) of small dipterans that were washed from the shoreline during the high tide. Detailed observations were made on flocks that assembled in early August. In the first flock, feeding activity extended over 140 min in the late morning to early afternoon of 1 August. This flock was initially composed of adult R. tridactyla feeding along 30 m of cobble beach at a distance of <1 m from shore. As before, there was a gentle surge that washed pupae and larvae from the cobble beach. Whitish larvae and black pupae were visible up to 10-15 m from shore. Within 30 min of initial feeding activity there were 19 adult R. tridactyla, and 12 adult and 3 first year L. schistisaugus. At 75 min there were 52 R. tridactyla and 21 L. schistisaugus vigorously picking larvae and pupae from surface film. Other species of marine birds were not observed. Agonistic interactions between kittiwakes and gulls were not observed. During the peak of foraging activity, feeding intensity by individual birds ranged from 17-31 dips per 30 sec interval (N = 5; 5 = 25). At about 135 min the flock began to disperse, and gulls departed prior to the kittiwakes. The final assemblage lasted for 90 min and was similar to those previously described, being composed of 71 adult R. tridactyla, and 12 adult and a young of the year L. schistisaugus. However, we also observed 3 ruddy turnstones (Arenaria interpres), 10 wood sandpipers (Tringa glareola), 4 common sandpipers (Actitis hypoleucos) and several white wagtails (Motacilla alba) simultaneously feeding among the cobbles in the splash zone adjacent to the larids. All species were feeding on dipteran larvae and pupae. Although all birds were in close proximity, we observed no agonistic interactions.

The effects of needle loss in coniferous forests in South-west Sweden on the winter foraging behaviour of willow tits Parus montanus

The foraging behaviour of the willow tit Parus montanus was studied in two coniferous forest areas in SW Sweden, showing high (H) and low (L) percentages of needle loss, respectively. The needle loss is presumed to be accelerated mainly by air pollution and leads to (1) thinning of the tree conopies which could make birds easier for predators to detect and (2) reduction in the abundance of arthropods, which are important food of wintering passerines. Willow tits foraging in pine Pinus sylvestris in the H-area spent proportionally more time scanning for predators and less time handling prey than individuals in the L-area. In the H-area the tits also joined larger mixed-species flocks which included more species. These responses are interpreted as increased time stress in damaged forest but nevertheless the birds showed no tendency to lower their body mass. The results are discussed in relation to winter survival and the consequences of needle loss for bird populations in coniferous forests.

Social System and Helping Behavior in the White-Banded Tanager (Neothraupis fasciata)

Banded Neothraupis fasciata were found in both unispecific groups and mixed-species flocks throughout the year, in cerrado (savanna) near Brasilia, Brazil. Groups with a mean of 3.0 individuals defended permanent territories. Territory size seemed to approach home-range size which was estimated for one group as being 4.3 ha. Some banded nestlings remained with their parents until the onset of the first reproductive season after birth. Pairs were occasionally assisted by helpers, which were either males or females, apparently offspring from prior years. Helpers had multiple roles, such as assisting in feeding nestlings, assisting in territorial defense, and acting as sentinels, which may increase protection against predation.

The influence of sexual dimorphism on kleptoparasitism of Blue-footed Boobies by Brown Boobies

In the Canal de Ballenas, Gulf of California, Mexico, we observed Brown Boobies (Sula leucogaster) steal food from Blue-footed Boobies (Sula nebouxii), a previously undescribed kleptoparasitic interaction. Brown Boobies were the primary kleptoparasite of Blue-footed Boobies. Of the 28 attacks recorded we determined the sex of the Brown Boobie 16 times, and in all cases the Brown Boobies were females, the larger of the two sexes. Kleptoparasitism may be facilitated by the juxtaposition of these two species, with slightly different foraging strategies, in mixed-species feeding flocks.

Mixed species flocking of tits (Parus spp.): a field experiment.

We tested two general models of flocking behaviour, namely the antipredation model and foraging efficiency model on mixed-species tit flocks (Parus spp.). After food addition the size of mixed-species flocks was significantly less than in the control samples. In the presence of extra food significantly more birds were observed either in monospecific flocks or solitary, than during the control observations. In the presence of a living predator the birds foraged in larger mixed-specifies flocks than during the control observations. In addition, the social behaviour of Great Spotted Woodpecker, Middle Spotted Woodpecker and Nuthatch shifted to mixed-specific flocking. The size of monospecific flocks was independent of both treatments. The density of birds increased significantly after food addition, while in the predator presence the birds tended to leave the forest. These results support the view that both the antipredation model and foraging efficiency model seem to be valid for mixed-species flocking. However, in the case of monospecific flocks, the territory maintenance could be the most important factor.

A STUDY OF SOME BIRD PARTIES IN ZAMBIA

Summary Nefdt, R.J.C. 1989. A study of some bird parties in Zambia. Ostrich suppl. 14: 27–32. An account is given of the specific and individual composition of bird parties (mixed-species flocks) associated with Brachystegial/Julbernardia woodland near Lusaka, Zambia. Of the 40 species in these flocks, the Forktailed Drongo was the most common, occurring in all the bird parties, and on average present 97% of the time in any one flock. Flocks travelled faster in more open vegetation and the routes taken were always different. Certain species tended to lead the bird parties, but their presence was not essential for the maintenance of the bird party. Some species joined parties infrequently, but once participating, remained attached throughout the observation time. It is concluded that several species, together or separately, influence the direction and speed of bird parties. They may also help bring different species together. By participating in such flocks, birds can reduce their vigilance against predato...

ASPECTS OF THE FORAGING BEHAVIOUR OF SOME INSECTIVOROUS BIRDS IN THREE TRANSVAAL INDIGENOUS EVERGREEN FORESTS

Summary Earle, R.A. 1989. Aspects of the foraging behaviour of some insectivorous birds in three Transvaal indigenous evergreen forests. Ostrich suppl. 14: 71–74. The influence of vegetation structure on the foraging height of seven bird species occurring in three different Transvaal forests was investigated. The distribution of suitable foraging sites, either leaves, twigs, branches or open sallying areas, was apparently the important factor in determining the foraging height of any species. The formation of six bird parties was observed. The Cape Batis Batis capensis and the Yellowthroated Warbler Seicercus ruficapillus always formed the two-species parties; other species probably joined the parties whenever they encountered them. Some individual birds joined such parties on a regular basis. The formation of bird parties was probably an adaptation to conditions during winter when the arthropod food supply was at its lowest.

Size differences in migrant sandpiper flocks: ghosts in ephemeral guilds.

Scolopacid sandpipers were studied from 1980 until 1984 during spring migration in North Dakota. Common species foraging together in mixed-species flocks differed in bill length most often by 20 to 30 percent (ratios from 1.2:1 to 1.3:1). Observed flocks were compared to computer generated flocks drawn from three source pools of Arctic-nesting sandpipers. The source pools included 51 migrant species from a global pool, 33 migrant species from a Western Hemisphere pool, and 13 species that migrated though North Dakota. The observed flocks formed randomly from the available species that used the North Dakota migration corridor but the North Dakota species were not a random selection from the Western Hemisphere and global pools of Arctic-nesting scolopacid sandpipers. In short, the ephemeral, mixed-species foraging flocks that we observed in North Dakota were random mixes from a nonrandom pool. The size-ratio distributions were consistent with the interpretation that use of this migration corridor by sandpipers has been influenced by some form of sizerelated selection such as competition.

Weather-Dependent Mixed-Species Flocking during the Winter

Weather-Dependent Mixed-Species Flocking during the Winter

Observations of a Mixed-Species Flock of Birds Foraging on Euphausiids near St. Matthew Island, Bering Sea

We observed mixed-species flocks of birds foraging for euphausiids near Cape Upright, St. Matthew Island. Murres (Uria spp.) predominated, and the number present was equivalent to 79% of the murres breeding at Cape Upright, or 11% of the total St. Matthew population. All bird species actively feeding were catching the euphausiid Thysanoessa raschii. SCUBA divers determined that murres were diving deeper than 30 m; schools of euphausiids were not observed above that depth. Injured and disoriented euphausiids were present near the surface where surface-feeding Black-legged Kittiwakes (Rissa tridactyla) captured them.

Badge, Body and Testes Size in House Sparrows Passer domesticus

Pdysi, H. 1985. Changes in predator surveillance in a foraging great tit Parus major in response to presence and group size of yellowhammers Emberiza citrinella. Ornis Fennica 62: 138-140. 1986a. Foraging niche shifts in multispecies dabbling duck (Anas spp.) feeding groups: harmful and beneficial interactions between species. Ornis Scand. 17: 333-346. 1986b. Species composition and size of dabbling duck (Anas spp.) feeding groups: are foraging interactions important determinants? Ornis Fennica 63: 33-41. 1987. Feeding-vigilance trade-off in the teal (Anas crecca): effects of feeding method and predation risk. Behaviour (In press). Sullivan, K. A. 1984. Information exploitation by downy woodpeckers in mixed-species flocks. Behaviour 91: 294311. Thompson, D. B. A. and Barnard, C. J. 1983. Anti-predator responses in mixed species associations of lapwings, golden plovers and gulls. Anim. Behav. 31: 585-593. and Thompson, M. L. P. 1985. Early warning and mixed species associations: the 'Plover's Page' revisited. Ibis 127: 559-562.

Copying of Foraging Locations in Mixed-Species Flocks of Temperate-Deciduous Woodland Birds: An Experimental Study

We examined copying of foraging locations among the members of mixedspecies foraging flocks of deciduous woodland birds. We used 10 captive flocks, each consisting of a male and a female Downy Woodpecker (Picoides pubescens), a male and a female White-breasted Nuthatch (Sitta carolinensis), three Tufted Titmice (Parus bicolor), and two Carolina Chickadees (P. carolinensis). Low-ranking individuals were less likely than dominants to take even a single mealworm (Tenebrio sp.) from a cryptic food supply, but when they did take at least one mealworm they tended to do so more quickly than dominants. Subordinates were quicker to follow a conspecific than a dominant heterospecific in extracting a mealworm from the cryptic supply. We examined how two types of learning, local enhancement and social facilitation, might enhance food finding among these four species. Compared to higher-ranking individuals, subordinates were more likely to generalize to a similar foraging site (social facilitation) than to go to the exact site of a food find (local enhancement). Our results also suggest that the intraspecifically subordinate chickadees and titmice may be at an advantage in mixed-species rather than single-species flocks because dominant heterospecifics may interfere with their foraging less than may dominant conspecifics.

Body Size, Interspecific Interactions, and Use of Foraging Sites in Tits (Paridae).

In mixed-species flocks, the heavier tit species forage in the inner tree parts, while the smaller species exploit food items of the outer canopy. Using aviary experiments we studied the relative importance of two possible explanations for body size-foraging site correlation. The first hypothesis is that larger bodied tits are more efficient than smaller ones in exploiting the inner tree parts, while the reverse would be true in the outer canopy. However, the heavier species, the Willow Tit Parus montanus, was not more efficient in food searching in the inner tree parts than the smaller species, the Coal Tit Parus ater. The second hypothesis is based on interference competition with the socially dominant (heavier) species selecting the most profitable foraging sites, and forcing the smaller species to less rewarding places. In fact, in confrontation experiments only individuals of the smaller species changed their foraging sites in the presence of an individual of the other species in the aviary. In sum, body size influences social dominance relations and thereby relegates the smaller species to poorer foraging sites, but presumably gives them an advantage in exploitation competition via reduced energy demands for basal metabolism.

Composition and Temporal Variation of Flocks in the Sierra Nevada

The size and species composition of bird flocks in a mixed-conifer forest of the western Sierra Nevada was nearly identical over three winters. Golden-crowned Kinglets (Regulus satrapa), Chestnut-backed Chickadees (Parus rufescens), and Red-breasted Nuthatches (Sitta canadensis) had the highest number of individuals/flock. Kinglets and nuthatches were the most frequent flock members, although they occurred in only 28% and 20% of all flocks, respectively. Most species formed monospecific flocks, although they more often occurred in mixed-species flocks. Although flock size was significantly greater in early winter than in middle and late winter, the number of species/flock did not vary temporally. No meaningful correlations between flock composition and weather conditions were evident. Differences in flock composition between this and other studies resulted from the relatively high frequency of nuthatches found in our flocks. In addition, flock composition was apparently influenced greatly by habitat. The anti-predator and foraging efficiency models emphasized in the literature are evaluated, and a framework for a more complete testing of causes of flocking discussed.

Changes in the flocking behaviour of wintering English titmice with time, weather and supplementary food

Over the course of one winter, the food supply of birds living in a deciduous woodland in southern England was supplemented and unsupplemented during alternating periods. In the presence of substantial predation pressure from hawks, the sociality of blue tits, Parus caeruleus, and great tits, P. major, showed significant partial correlations with several weather and temporal factors when the woodland was unsupplemented. Such correlations between social behaviour and abiotic factors diminished significantly when the birds had access to extra food. Blue tits and great tits without access to supplemental food flocked significantly more often with other species while foraging than when they were food-supplemented. Long-tailed tits, Aegithalos caudatus, ignored the artificial food and foraged in mixed-species flocks to the same extent in both unsupplemented and food-supplemented periods. Results disprove the hypothesis that mixed-species foraging groups are caused by increased predation protection alone, and they support the hypotheses that mixed-species foraging groups are caused by increased foraging efficiency alone or by a combination of increased foraging efficiency and increased protection from predators.

A Description of Mixed-Species Insectivorous Bird Flocks in Western Mexico

Insectivorous bird flocks were observed in all types of forested habitats during the nonbreeding season in western Mexico. The species composition of flocks changed markedly and predictably among five categories of habitat type. The average number of species per flock in lowland habitats was 4.7, while a mean of 18.6 species participated in highland flocks, ranking the latter among the most species-rich flocks in the world. The mean proportion of the local insectivorous species that participated in mixed-species flocks was significantly greater in the highlands (61.3%) than in the lowlands (24.6%). About half of the flock participants in both undisturbed lowland and highland habitats were north temperate migrants, ranking west Mexican flocks among the most migrant-rich in the world as well. In highland flocks, the maximum number of individuals per attendant species was generally two to three, but there were often six to twelve individuals belonging to each of several nuclear species. The lowland deciduous forest flocks seemed to lack nuclear species.

Mixed-species flocking of forest birds on Little Barrier Island

Abstract Three aspects of mixed-species flocking of forest birds on Little Barrier Island were investigated. Whiteheads, fantails, parakeets, and grey warblers occurred more often in flocks than in “non-flocking” situations. Whiteheads were the main lead species, although parakeets formed groups within flocks and occasionally appeared to lead. Whitehead clumps defined the flock centre; only fantails were found commonly in the centre with whiteheads. Birds other than whiteheads generally orientated below or to the side of their nearest neighbours. We suggest that mixed-species flocking is a significant factor influencing the structure of forest bird communities in New Zealand during winter.

The Participation by Cuckoos in Mixed-Species Flocks of Insectivorous Birds in South-Eastern Australia

(1986). The Participation by Cuckoos in Mixed-Species Flocks of Insectivorous Birds in South-Eastern Australia. Emu - Austral Ornithology: Vol. 86, No. 4, pp. 249-253.