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
Comentarios
https://www.ilri.org/research/facilities/kapiti-research-station-wildlife-conservancy
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...
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...
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