SPECIES

Purple Martin Progne subis Scientific name definitions

Charles R. Brown, Daniel A. Airola, and Scott Tarof
Version: 2.0 — Published September 10, 2021

Diet and Foraging

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Feeding

Main Foods Taken

Flying insects at all times of the year.

Microhabitat For Foraging

Aerial, often at altitudes of at least 50 m, and higher than other swallows. Using altitude loggers, birds in Oklahoma flew to an average maximum height per bird of 849 m ± 362 SD; one foraging bird reached 1,889 m with others foraging as low as 6 m (167). Because of the foraging altitudes, foraging individuals are seen relatively infrequently, except in late afternoon and near dusk, when birds feed low and close to nest sites. Birds presumably range over habitats immediately surrounding the nest site, although there is no information on typical travel distance while foraging. In Illinois, foraging birds preferred fallow fields (about 4 birds/40 ha), followed in descending order by shrub areas, oat fields, soybean fields, alfalfa fields, and cornfields (168). Cold, rainy weather in spring forces individuals, especially migrants, to feed low over ponds and lakes, apparently in pursuit of aquatic emergent insects along the water surface (CRB).

Food Capture and Consumption

Diurnal forager, pursuing and catching insects in flight. Very rarely may glean insects off foliage or alight on the ground to take caterpillars (169), or skim insects off a water surface (170).

Does not generally feed in groups. A paired male and female often feed together, although this behavior probably reflects only mate-guarding by the male (see Behavior: Sexual Behavior). The contention by Johnston and Hardy (171) that Purple Martin feeds in groups is unsupported by observations of foragers in northern Texas (CRB). Rarely, birds converge on swarms or mass emergences of insects (CRB), perhaps using local enhancement cues from other foragers. There is no evidence that colonies serve as information centers (CRB). Intervals between foragers' prey captures near a northern Texas colony tended to be uniform (CRB), suggesting that this species typically feeds on dispersed and singly captured insects and not on insect aggregations (cf. 172). There is no evidence of specific food-finding calls, such as in Cliff Swallow (Petrochelidon pyrrhonota; 127), despite Johnston and Hardy's (171) assertion that foragers may call to maintain a foraging flock.

Before egg-laying begins and after the nestlings fledge, birds feed throughout the day in long bursts and may spend the entire afternoon away from the nest sites. After egg-laying begins, birds feed in more frequent and shorter bursts and are not absent from the colony for prolonged periods at any time of the day. Nonbreeding and post-breeding birds range up to at least 48 km from late-summer roosts while foraging during the day (162). Nothing is known about foraging behavior during winter.

Does not attempt to forage when air temperature is below ~9°C, because of scarcity of flying insects, and may require temperatures of at least 13°C to survive for prolonged periods (173). Martins foraged in winds of up to 10 km/hr but reduced activity at higher wind speeds, presumably due to reduction in aerial insect prey (174). Does not forage during rain regardless of temperature. During cold weather, feeds in business districts of towns, darting among cars and perching on wires, buildings, and traffic signals (Kansas: 175; Nebraska: CRB). Presumably, warmth generated by cars and asphalt attracts insects.

Diet

Major Food Items

Insects taken probably reflect local availability and vary across the breeding season (176). Total of 57 insect families found in a diet study in Kansas (176); at least 38 in Oklahoma (167); and 14 in Alberta (177). Included were beetles (Coleoptera), true bugs (Hemiptera), flies (Diptera), dragonflies and damselflies (Odonata), leafhoppers (Homoptera), grasshoppers and crickets (Orthoptera), butterflies and moths (Lepidoptera), wasps and bees (Hymenoptera), caddis flies (Trichoptera), and spiders (Araneida). In Texas, sometimes feeds on cicadas (Homoptera: Cicadidae), despite the enormous size of these insects, although parents have difficulty transferring them to the young (178). Has also been seen feeding on monarch butterflies (Danaus plexippus) in Wisconsin (179), winged termite (Isoptera) and mayfly (Ephemeroptera) emergences in Texas and Indiana (170, CRB), and forest tent caterpillars (Malacosoma disstria) in Minnesota, in the latter case by gleaning them from foliage (169).

Often picks up small bits of gravel to aid digestion of insect exoskeletons (180, 181). Sometimes feeds on crushed eggshells provided by humans (149) or other calcium-rich items in the environment (182), probably for grit and as a calcium supplement. Nestling growth rates are not increased significantly by calcium supplementation (182). Ingestion of clam (Hiatella arctica) shells occasionally kills nestlings (183).

Despite advertising claims by birdhouse manufacturers that martins routinely eat ≥ 2,000 mosquitoes/d (184), no credible evidence that this species routinely eats any mosquitoes (Diptera: Culicidae) (185). Feeds high and during daylight hours, in contrast to mosquitoes, which fly low and mostly at night (185).

Quantitative Analysis

In Kansas (176), the most common family taken was Scarabaeidae (scarab beetles), followed by Curculionidae (snout beetles), Carabidae (ground beetles)—all Coleoptera; Aphididae (aphids; Homoptera); Corimelaeninae (ebony bugs; Thyreocoridae, Hemiptera); Ichneumonidae (ichneumons; Hymenoptera) and Tipulidae (crane flies; Diptera). Diet varied across the breeding season: dipterans and homopterans were most common early in the season; hemipterans, lepidopterans, and hymenopterans were more common later; and coleopterans were taken throughout.

In Alberta (177), the most common family taken was Aeshnidae (darners: order Odonata), followed by Syrphidae (syrphid flies; Diptera), Nymphalidae (brush-footed butterflies; Lepidoptera), Chironomidae (midges; Diptera), Siricidae (horntails; Hymenoptera), Formicidae (ants; Hymenoptera), Cerambycidae (long-horned beetles; Coleoptera), Libellulidae (common skimmers; Odonata), and Coenagrionidae (narrow-winged damselflies; Odonata). Nymphalidae and Syrphidae differed significantly in occurrence between seasons in Alberta.

In Beal's (172) study of samples taken throughout North America and probably in different years, the order Hymenoptera (including Apidae [bees]) was most frequent (23%); followed by Diptera, including Tipulidae, Muscidae (muscid flies), and Asilidae (robber flies), 16%; Odonata, 15%; Hemiptera and Homoptera, including Pentatomidae (stink bugs), Membracidae (treehoppers), and Corimelaenidae, 14.6%; Coleoptera, including Carabidae, Scarabaeidae, and Curculionidae, 12.5%; Lepidoptera, 9.4%; and Orthoptera, 1.1%. Lepidopterans and odonates tend to be taken later in the summer (172, CRB).

In Oklahoma (167), 5 species of insects accounted for 87% of the prey consumed, with martins feeding extensively on aerial stages of social insects (ants, termites, and bees), with ants accounting for over 79% of hymenopteran prey items and 38% of the total biomass. Many of the ants taken were red imported fire ant (Solenopsis invicta) (186).

In Oregon (187), Diptera were the most common prey items by biomass in coastal, open water, and forested areas (18%, 33%, and 28% respectively). Other orders among the top three in biomass consumed in different habitat types included Hemiptera (in coastal and forested areas), Orthoptera (in coastal areas), Coleoptera and Trombidifera (near open water), and Hymenoptera (in forest).

Food Selection and Storage

No information.

Nutrition and Energetics

Little information. Modelling suggests that fall migration is the most energetically expensive period of the annual cycle (188).

Metabolism and Temperature Regulation

Expends an average 3.5 kcal/h in flight with carbon dioxide production of 23.7 mM /h (189). This was believed to represent energy expenditure while foraging, although the experimental design in which birds were transported 160 km from their nests, released, and recaptured after homing back to their nest sites, may not have measured true foraging costs if displaced birds flew straight back without feeding (see Demography and populations: range). Mean daily energy expenditure, determined from doubly labeled water experiments for 2 females feeding nestlings was 39.9 and 43.9 kcal, respectively; for 2 males not consistently feeding nestlings, 31.2 and 34.2 kcal, respectively (190).

Birds gape and pant when hot. Females sometimes soak the belly feathers by bathing, apparently to aid cooling of nestlings still being brooded (191); belly-soaking may also cool the adults themselves. In cold weather that forces individuals to go without food for > 48 h, birds often of same sex huddle together on porches of birdhouses, and up to 10 may pack themselves together inside a single nest cavity (173). Huddling presumably retards loss of body heat.

Drinking, Pellet-Casting, and Defecation

Drinks exclusively in flight, by skimming the water surface and lapping up water with the lower mandible. Adults fly out from the nest several meters to defecate. Not known to pellet cast.

Recommended Citation

Brown, C. R., D. A. Airola, and S. Tarof (2021). Purple Martin (Progne subis), version 2.0. In Birds of the World (P. G. Rodewald, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bow.purmar.02