Diet of the Maasai ostrich (Struthio camelus massaicus) on the Athi-Kapiti plains, Kenya

Struthio camelus massaicus (https://www.inaturalist.org/observations?taxon_id=322201)

STUDY AREA AND METHODS

Location:
Wildlife Ranching and Research, which was later renamed Swara Plains Conservancy (https://www.perplexity.ai/search/What-is-the-UV5KdNn1SCaEOGLoyrCChw), and was recently incorporated into Nairobi National Park.

Time of fieldwork:

Intermittently during 1987-1989

RESULTS

The following are the genera recorded eaten by the Maasai ostrich, either found in adult stomachs (n = 10 individuals) or observed in 17 foraging bouts by one habituated adult individual.

Percentages refer to mass eaten in the first instance, and incidence in stomachs in the second instance.

Asterisks (*) indicate those families also recorded to be eaten frequently during the direct observations.

All families were recorded in the diet of this population of the Maasai ostrich in both the dry and rainy seasons, except Balanitaceae (eaten mainly in the dry season), and Cyperaceae and Acanthaceae (eaten mainly in the green season).

  • *Asteraceae (Aspilia, Galinsoga, Tagetes, Bidens) 23.0% (0-90); 60%
  • *Malvaceae (Hibiscus, Pavonia, Melhania,?Abutilon) 17.6% (5-40); 90%
  • *Poaceae (Sporobolus, Cynodon, Eragrostis) 15.7% (0-75); 80%
  • *Commelinaceae (Commelina) 14.5% (0.1-60); 100%
  • *Fabaceae (Indigofera, Crotalaria, Dolichos, Trifolium) 6.8% (0-30); 20%
  • Solanaceae (Solanum) 5.2% (0-20); 50%
  • Balanitaceae (Balanites) 5.2% (0.1-22); 90%
  • Mimosaceae (??Vachellia) 2.7% (0-20); 50%
  • Asphodelaceae and Asparagaceae (Aloe, ?Albuca) 1.8% (0-6); 40%
  • Euphorbiaceae (Euphorbia) <0.5% (0-2); 30%
  • Cucurbitaceae <0.1% (0-0.5); 10%
  • Cyperaceae <0.1% (0-0.1); 10%
  • Lamiaceae (?Plectranthus, ?Ocimum) <0.1% (0-0.1); -
  • Tiliaceae (Grewia) <0.1% (0-0.2); 10%
  • Convolvulaceae (Ipomoea) <0.1% (0-0.1); -
  • Acanthaceae (Justicia, Crossandra) <0.1% (0-0.1); -
  • Polygonaceae (Oxygonum) -
  • Amaranthaceae (Achyranthes) -
  • unidentified 6.8% (0-25); 100%

Aspilia mossambicensis:
https://www.inaturalist.org/taxa/147342-Aspilia-mossambicensis

Galinsoga parviflora:
https://www.inaturalist.org/taxa/48178-Galinsoga-parviflora

Tagetes minuta:
https://www.inaturalist.org/taxa/79313-Tagetes-minuta

Bidens pilosa:
https://www.inaturalist.org/taxa/50203-Bidens-pilosa

Hibiscus flavifolius:
https://www.inaturalist.org/taxa/343058-Hibiscus-flavifolius

Pavonia:
https://www.inaturalist.org/observations?place_id=10957&subview=map&taxon_id=52356&view=species

Abutilon:
https://www.inaturalist.org/observations?place_id=10957&subview=map&taxon_id=53864

Commelina:
https://www.inaturalist.org/observations?place_id=10957&subview=map&taxon_id=52893

Indigofera:
https://www.inaturalist.org/observations?place_id=10957&subview=map&taxon_id=83365&view=species

Crotalaria:
https://www.inaturalist.org/observations?place_id=10957&subview=map&taxon_id=123472&view=species

Dolichos:
https://www.inaturalist.org/observations?place_id=56881&subview=map&taxon_id=139262&view=species

Trifolium:
https://www.inaturalist.org/taxa/55745-Trifolium-repens

Solanum:
https://www.inaturalist.org/observations/215986766

Balanites glabra:
https://en.wikipedia.org/wiki/Balanites_glabra

Grewia:
https://www.inaturalist.org/observations?place_id=10957&subview=map&taxon_id=68716&view=species

Ipomoea:
https://www.inaturalist.org/observations?place_id=10957&subview=map&taxon_id=52346&view=species

Justicia:
https://www.inaturalist.org/observations?place_id=10957&subview=map&taxon_id=50152

Crossandra:
https://www.inaturalist.org/observations?place_id=10957&subview=map&taxon_id=201316&view=species

Melhania:
https://www.inaturalist.org/observations?place_id=7042&subview=map&taxon_id=185886&view=species

Oxygonum:
https://www.inaturalist.org/observations?place_id=7042&subview=map&taxon_id=553830&view=species

Achyranthes:
https://www.inaturalist.org/observations?place_id=10957&subview=map&taxon_id=142081

Albuca:
https://www.inaturalist.org/observations?place_id=7042&subview=map&taxon_id=119218

Aloe:
https://www.inaturalist.org/observations?place_id=10957&subview=map&taxon_id=71956

Plectranthus:
https://www.inaturalist.org/taxa/430498-Plectranthus-fruticosus

Ocimum:
https://www.inaturalist.org/observations?place_id=10957&subview=map&taxon_id=61399&view=species

Silica content in diet of ostrich

As at 1 May 1989: at least one-third of the non-grass genera in the diet are rich in silica.

Rich in silica:
Aspilia, Justicia, Crossandra, Commelina, Pavonia, Cucumis, all grasses, Salvadora

Moderately rich in silica:
Galinsoga, Ipomoea, Hibiscus, Heliotropium

Poor in silica:
Balanites, Euphorbia, Solanum, Vachellia, Monechma

Unknown as yet:
Melhania, Indigofera

Publicado el mayo 15, 2024 10:49 TARDE por milewski milewski

Comentarios

The study area enjoyed good rainfall during the December (normally already dry) preceding the direct observations, followed by a further 87 mm (= 17% of mean annual rainfall) spread through January 1989. The short rains lasted until 22 January 1989.

The habituated study-individual of the Maasai ostrich sometimes appeared to ignore food theoretically attractive to an omnivore. Succulent items (e.g. Solanum fruit), probably essential under arid conditions (Robinson and Seely 1975, Williamson 1987) were possibly not particularly attractive because of the favourable season and the bird's unlimited access to...

Publicado por milewski hace alrededor de 2 meses

Note on methods:

In the green season, I took several boluses dominated by leaves and shoots, and I tallied the number of pecks on leaves and shoots per bolus. The results were mean = 45 pecks on leaves and shoots per bolus dominated by leaves and shoots in the green season (n = 29: 67.31.56.95.72.39.61.36.31.68.33.44.24.34.75.14.56.45.26.33.41.60.47.38.20.20.47.34.57.).

Similarly for grass in the dry season:
mean = 48 pecks per bolus
(n = 21: 21.51.32.43.81.81.45.33.40.86.34.23.50.75.60.39.37.63.43.16.58.)

I did not test these statistically. However, it is fairly obvious that the above means do not differ. I conclude that the peck-sizes of leaves and shoots were about the same as those of grass...

Publicado por milewski hace alrededor de 2 meses

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Publicado por milewski hace alrededor de 1 mes

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