Cassin's Sparrow

Peucaea cassinii


Diet and Foraging

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Cassin's Sparrow with prey item.

Main foods taken include insects during the nesting season, and weed and grass seeds during the nonbreeding season.

© Steven Mlodinow , Colorado , United States , 4 June 2017


Main Foods Taken

Cassin's Sparrow consumes insects during the nesting period, and the seeds of forbs and grasses during the nonbreeding period.

Microhabitat for Foraging

Forages on or near the ground.

Food Capture and Consumption

From Wolf (3): Forages almost entirely on ground. Hops on ground gleaning seeds and insects from relatively open areas at base of plants. During winter, most food items are picked up directly from surface of ground. In summer, many insects are plucked from standing plant stems, with some seeds also collected from standing seed heads. Foraging in mesquite and other shrubs is indicated by diet items, especially when feeding young. During the breeding period in western Texas (29): an unmated male spent 64% of day feeding or walking on ground (Table 2), decreasing to 19% during incubation and parental care period. Female spent 93.5% of day feeding/walking during preincubation period, increasing to 97–98% of time off nest during incubation and nestling care periods, and decreasing to 90% during fledgling care. Fledglings feed mostly by foliage gleaning, and seldom gleaned from the ground (29). Cassin's Sparrow may have a significant impact on grasshopper populations (104).


Stomach contents of 10 adults collected in late June–early July included 52% animal, 48% plant material (3). Five migrants (season not specified) had 97% animal matter in stomach; whereas one bird in Arizona collected in January had only seeds and grit (3). Oberholser (20) and Wolf (3) listed the following diet items: grasshoppers (Orthoptera); caterpillars (Lepidoptera); true bugs (Hemiptera); ants, bees and wasps (Hymenoptera); weevils (Coleoptera); spiders (Arachnida); and snails (Gastropoda) in warm-weather months; seeds of Common Chickweed (Stellaria media), plantain (Plantago sp.), woodsorrel (Oxalis sp.), sedge (Carex spp.), panicgrass (Panicum spp.) and other grasses, and sorghum (Sorghum sp.) during winter. In spring, eats flower buds of plants such as Knifeleaf Snakewood (Condalia spathulata) in Arizona (J. Marshall in Willliams and LeSarrier [78]). Exclosure experiments in southern Arizona demonstrated that insectivorous birds (with Cassin’s Sparrow being most common) significantly reduced numbers of grasshoppers feeding on common weed species (105).

At one nest in southeastern Arizona (4–13 August 1983), 197 of 208 prey items delivered to young by parents were grasshoppers (K. Jepsen-Innes, unpublished data), including the following species: Psoloessa texana, P. delicatula, Helialula rufa, Eritetix simplex, Ageneotettix deorum, Amphitornus coloradus, Cordillacris crenulata, Parapomala wyomingensis, Syrbula montezuma, Aulocara femorata, and Opeia species. Parents at two nests delivered to young an average of 1.9 grasshoppers/10 min ± 0.59 SD (range 1.0–2.6, n = 8 observation periods). Observations covered 988 min, both evening and afternoon, 4–13 August 1983 (K. Jepson-Innes, personal communication; RKB). Parents also delivered additional prey (numbers summed over same 8 observation periods): praying mantis (Mantodea, 2); caterpillar (Lepidoptera, 4); red ant (Hymenoptera, 1); other larvae (5); and cricket (Orthoptera, 1).

Food Selection and Storage

No information.

Nutrition and Energetics

Schnase et al. (7) examined time budgets of breeding Cassin's Sparrows, and used published estimates of energetic parameters for Savannah Sparrow (Passerculus sandwichensis) and other passerines to estimate energy needs. The energetics model predicted that male Cassin's Sparrow requires 88 kJ/d during breeding season. Assuming an assimilation efficiency of 75%, the study suggested that males must ingest 117 kJ/d of dry food. Insects contain average of 23.2 kJ/dry gram mass. Thus, male sparrows must consume 5 g dry insect matter/d. The water content of insects is about 74%, thus male Cassin's Sparrow needs 19 g of fresh arthropods/d to supply daily energy needs during summer. Mean estimate varies from 13 to 26 g during different parts of the breeding cycle. Similar analysis for female yields estimate of 15 g of fresh arthropods to provide 70 kJ/d. Assumption that Savannah Sparrow energetic estimates were appropriate for estimating Cassin's Sparrow energy needs was untested.

Male in breeding season has greater total power consumption than female (male:female ratio 1.6: 1) due to territorial and mate defense (7). Male costs increase with nest failure (ratio 1.9: 1) due to resumption of skylarking by male. Schnase et al. (7) model predicted average power consumption of 88 kJ/d, while Walsberg (106) allometric model predicted 82.2 kJ/d. Similar model predicts power consumption of Savannah Sparrow as 95.1 kJ/d. Sensitivity analysis of Schnase et al. (7) model suggests model most responsive to error in estimates of basal metabolic rate and body mass.

Based entirely on model for nestling Savannah Sparrows, Schnase et al. (7) estimated that 716 kJ of energy must be delivered by parents during 9-day nestling period. Equivalent to 158 g of insects. Since female needs 117 g for her own nutritional needs, female must increase foraging intake by 135% if feeding young on her own. Schnase et al. (7) did not see males feed nestlings although male feeding can be common (107, 78, RKB).

Drinking, Pellet-Casting, and Defecation

Schnase (29) observed a Cassin's Sparrow drinking from a small pool immediately after a rain, but few other observations of drinking behavior (78, 20). Often nests far from open sources of water.

Recommended Citation

Dunning, J. B., Jr., R. K. Bowers Jr., S. J. Suter, and C. E. Bock (2018). Cassin's Sparrow (Peucaea cassinii), version 2.0. In The Birds of North America (P. G. Rodewald, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA.