29 May, 2024

Evolutionary and ecological strategy of whiteyes and silvereyes (Zosterops)

Zosterops spp. (whiteyes and silvereyes) are odd in several ways.

They are

Crucial is the observation that Zosterops oddly combines a brush-tipped tongue with a short beak (https://www.perplexity.ai/search/Please-list-all-P5272Q3URqe3IcoI547GAg).

In this Post, I introduce the idea that a central evolutionary strategy of Zosterops is to be simultaneously

Most small birds participating in ornithophily have long beaks (https://pubmed.ncbi.nlm.nih.gov/36062802/ and https://evolution.berkeley.edu/convergent-evolution-its-for-the-birds/). These are inefficient for gleaning aphids.

Furthermore, aphids tend to be scarce in the nutrient-poor, fire-prone ecosystems typically associated with Meliphagidae and Promeropidae. In Australia, aphids are generally replaced by psyllids (https://en.wikipedia.org/wiki/Psyllid) and other armoured forms of sap-sucking Hemiptera (https://en.wikipedia.org/wiki/Hemiptera), predated mainly by small passerines with specialised, broad beaks (https://en.wikipedia.org/wiki/Pardalote and https://en.wikipedia.org/wiki/Weebill).

Long-beaked, nectarivorous birds do take remarkably small insects routinely, but mainly by hawking (https://en.wikipedia.org/wiki/Hawking_(birds) and https://researchportal.murdoch.edu.au/esploro/outputs/other/The-possible-ecological-significance-of-hawking/991005541828107891 and https://www.researchgate.net/publication/283793917_Ecology_of_Honeyeaters_Meliphagidae_in_Western_Australian_Eucalypt_Woodlands_I_Resource_Allocation_Among_Species_in_the_Great_Western_Woodland_During_Spring and https://www.sciencedirect.com/science/article/abs/pii/S0003347205802295).

I suggest that Zosterops evolved as essentially a consumer of aphids and simultaneously the sugary secretions produced by aphids. This has helped the genus to succeed on islands, because the mutualism between aphids and the ants that protect them is widespread on Earth.

From this origin, Zosterops has been able to adapt to a remarkably wide range of ecosystems by means of certain 'lateral' applications of its basic nature. This has been done mainly behaviorally, as opposed to morphologically.

In other words, Zosterops has retained small body size and a consistent shape (including the beak) while being versatile in other ways. It has applied a single body-form to various niches.

In particular, Zosterops varies in

  • residency (sedentary vs nomadic vs migratory), albeit never a migrant between hemispheres,
  • diet (e.g. emancipated from aphids in Australia, where it takes sugary exudates from Eucalyptus and Acacia instead), and
  • mutualistic participation with plants in pollination and seed-dispersal.



Posted on 29 May, 2024 15:53 by milewski milewski | 3 comments | Leave a comment

28 May, 2024

The former - and nearly forgotten - commonness of the ring-necked dove (Streptopelia capicola) in Cape Town, South Africa

@adamwelz @jeremygilmore @tonyrebelo

While I was a teenager, growing up in Cape Town in the 'sixties, the ring-necked dove (Streptopelia capicola, https://www.inaturalist.org/taxa/2959-Streptopelia-capicola and https://thebdi.org/2022/03/08/cape-turtle-dove-streptopelia-capicola/) was the common indigenous columbid in this metropolitan area in South Africa (https://en.wikipedia.org/wiki/Cape_Town).

At that time, the red-eyed dove (Streptopelia semitorquata, https://www.inaturalist.org/taxa/2988-Streptopelia-semitorquata) was nominally present in Cape Town. However, I was unfamiliar with it or its call.

Today, the latter species is unquestionably the common member of its genus in Cape Town, with the erstwhile commonness of the former species nearly forgotten.

Two aspects of this species-replacement, which has been natural and spontaneous albeit ultimately anthropogenic, warrant mention here.

These are

  • how rapidly indigenous birds can adapt to changes in the environment at a biogeographical scale, altering their distribution, habitat, and population-density over a period of merely a few decades, and
  • how even major avifaunal changes, in regions well-populated by naturalists and ornithologists, can come to be forgotten because they happen gradually enough that, at each stage of the process, the status quo tends to be taken for granted.

Such changes, although remarkable in hindsight, can seem so mundane that naturalists and scientists do not bother to write them down for posterity. The substitution has been obvious to me over my lifetime. However, there is a risk that the fact of it may fail to be transmitted to subsequent generations.

What is simply a matter of experience for me may come, in future, to be merely some unsubstantiated historical hypothesis.

So, for the record:

  • which readers remember a time when the call of the ring-necked dove was an everyday sound in the suburbs of Cape Town? and
  • does anyone know of any publication that has documented this switch from one congener to another?
Posted on 28 May, 2024 15:58 by milewski milewski | 2 comments | Leave a comment

27 May, 2024

Ecology of termite mounds in Kruger National Park

Posted on 27 May, 2024 23:13 by milewski milewski | 0 comments | Leave a comment

Portulacaria afra

Posted on 27 May, 2024 22:29 by milewski milewski | 0 comments | Leave a comment

Ecological differences between lookalike species of Zosterops in southwestern Australia and southwestern southern Africa

@tonyrebelo @jeremygilmore @ludwig_muller

Only five genera of passerine birds are indigenous to both southwestern Western Australia (https://en.wikipedia.org/wiki/Southwest_Australia) and the climatically and latitudinally similar southwestern Cape of South Africa (https://en.wikipedia.org/wiki/Western_Cape).

These are, in alphabetical order

In this Post I compare, ecologically, the following taxa:

The two taxa seem virtually identical in size and shape.

Furthermore, both of them eat fruit-pulp and nectar.

However, the emphasis/reliance seems different.

Zosterops v. capensis differs from its southwestern Australian congener in several ways.

Firstly, it relies on indigenous fleshy fruit-pulp (https://www.projectnoah.org/spottings/10432262), rather than the indigenous nectar with which Z. l. chloronotus is mainly associated (https://library.dbca.wa.gov.au/static/Journals/082168/082168-25.pdf).

Secondly, it is perennially resident, rather than migrating from temperate latitudes to the subtropics each winter.

In western South Africa, the subtropics are perennially occupied by a different species, viz. Zosterops pallidus (https://www.inaturalist.org/taxa/472771-Zosterops-pallidus).

Thirdly, Z. v. capensis seems particularly suited to dispersing and sowing the relatively small, arillate diaspores of Celastraceae, particularly

These plants lack counterparts in the flora of southwestern Australia.

Fourthly, Z. v. capensis lacks a certain mutualistic relationship with plants, as follows.

Zosterops lateralis pollinates various spp. of Acacia, indigenous to Australia, by being attracted to extrafloral nectaries, located on the foliage.

The bird pollinates the plants despite having a short beak. This is by virtue of accidentally rubbing against the yellowish pom-prom inflorescences - which do not produce nectar - as it moves through the shrub from one nectar-bearing leaf or phyllode to another (Sargent O H 1928 Reactions between birds and plants, Emu 27: 185-192 and https://www.researchgate.net/publication/253953794_Birds_as_pollinators_of_Australian_plants).

The above comparison raises two questions about Zosterops in the southwestern Cape of South Afirca, as follows.

  • Is any indigenous plant in the Cape Floristic Region (https://en.wikipedia.org/wiki/Cape_Floristic_Region) naturally pollinated by Z. v. capensis? and
  • Has Z. v. capensis taken to visiting the extrafloral nectaries of the various spp. of Acacia introduced anthropogenically to South Africa, thus helping to pollinate these plants?

Also please see https://www.inaturalist.org/journal/milewski/91030-extreme-seasonal-incidence-of-the-silvereye-zosterops-lateralis-chloronotus-in-autumn-of-2024-in-the-perth-metropolitan-area-western-australia-in-response-to-heat-and-drought#

Posted on 27 May, 2024 01:35 by milewski milewski | 17 comments | Leave a comment

26 May, 2024

Pictures worth a thousand words

Posted on 26 May, 2024 14:54 by milewski milewski | 0 comments | Leave a comment

The ostrich (Struthio camelus) as a quasi-ungulate, part 7















The following is a list of all the ungulates potentially coexisting with the ostrich, with their body masses (adult females) and metabolic body masses (https://www.perplexity.ai/search/Explain-the-concept-OzTlv1FeQ92LIlZ07kQsaw), both expressed in kg

** = true coexistors

Struthio camelus 110 27

Hippopotamus amphibius 1200 204
**Diceros bicornis 800 150
**Giraffa tippelskirchi 800 150
**Giraffa giraffa 800 150
**Giraffa camelopardalis 800 150
**Giraffa reticulata 800 150
**Syncerus caffer 400 89
Camelus dromedarius 350 81
**Equus grevyi 350 81
**Taurotragus oryx 300? 72? https://www.alamy.com/an-eland-bull-and-an-ostrich-sharing-a-watering-hole-in-southern-african-savanna-image235462173.html
**Equus quagga quagga & burchellii 290? https://www.african-safari-pictures.com/ostrich-pictures.html
Equus kiang 300?
**Equus hartmannae 275?
Equus somaliensis 250 63
Equus zebra 250 63
**Equus quagga boehmi 250 63 https://www.gettyimages.com.au/detail/photo/tanzania-zebra-herd-royalty-free-image/583742292?phrase=struthio+camelus+massaicus&adppopup=true
**Kobus ellipsiprymnus & defassa 240 61
Hippotragus equinus 220 57
**Strepsiceros strepsiceros 210 55
Equus hemionus kulan 200?
**Connochaetes albojubatus 180 49
**Connochaetes taurinus 180 49
Equus hemionus hemionus 150?
**Oryx gazella 150 43 https://www.flickr.com/photos/gridarendal/31282852533 and https://www.alamy.com/gemsbok-or-orix-antelope-and-an-ostrich-at-a-waterhole-kgalagadi-transfontier-park-south-africa-image448482611.html and https://pixabay.com/photos/ostrich-bird-antelope-oryx-running-63360/
**Oryx dammah 150 43
**Connochaetes mearnsi 140?
Hippotragus niger 140 41
**Alcelaphus caama 140 41
Alcelaphus buselaphus
**Alcelaphus cokii 125? 35
Alcelaphus lelwel
**Damaliscus lunatus 120 36
**Oryx beisa & callotis 120 36 https://navlovesm.pics/product_details/36430425.html
**Beatragus hunteri 100 32
Cervus elaphus 100 32
Addax nasomaculatus 100 32 taken as mf
**Connochaetes gnou 90 29
Hylochoerus meinertzhageni 85 28
**Ammelaphus imberbis 80 27
**Oryx leucoryx 80 27
**Damaliscus pygargus 70 24
Tragelaphus spekii & gratus 70 24 mf
Potamochoerus larvatus 50 19
Redunca arundinum 50 19
Ammotragus lervia 50 19
**Phacochoerus africanus 45 17
**Phacochoerus aethiopicus 45 17
**Aepyceros melampus 45 17
Dama dama 45 17
**Nanger granti 45 17 https://www.gettyimages.com.au/detail/news-photo/kenya-africa-medium-view-of-an-ostrich-near-an-antelope-in-news-photo/947611476?adppopup=true and https://www.flickr.com/photos/gridarendal/31282852533 and https://navlovesm.pics/product_details/47232597.html and https://navlovesm.pics/product_details/47232593.html
Nanger dama
**Nanger soemmeringi 40 16
**Redunca redunca 40 16
Capra nubiana 40 16
Arabitragus jayakari 40 16
Tragelaphus scriptus 35 14
Tragelaphus sylvaticus 35 14
**Litocranius walleri 35 14
Ammodorcas clarkei 35 14
Redunca fulvorufula 30 13
Antidorcas marsupialis 30 13 https://navlovesm.pics/product_details/47232591.html
Gazella leptoceros 25
**Eudorcas rufifrons 20 9
**Eudorcas thomsonii 20 9 https://navlovesm.pics/product_details/47232592.html and https://navlovesm.pics/product_details/36430428.html and https://www.gettyimages.com.au/detail/news-photo/kenya-africa-medium-view-of-an-ostriches-grouping-in-the-news-photo/947611526?adppopup=true
**Gazella 20 9
**Sylvicapra grimmia grimmia & steinhardti 20 9
**Gazella dorcas 15 8
**Sylvicapra grimmia caffra & & orbicularis 15 8
Ourebia ourebi 15 8 mf
Ourebia montana 15 8 mf
Sylvicapra grimmia campbelliae & hindei & madoqua & coronata & 10 6
**Raphicerus campestris 10 6 cs
Raphicerus melanotis & sharpei 8 5 Cs
Neotragus moschatus 5 3
**Madoqua 5 3
**Madoqua 4 3
Madoqua 3 2

Posted on 26 May, 2024 01:37 by milewski milewski | 26 comments | Leave a comment

24 May, 2024

An extinct canid ('Canis rubronegrus') hiding in plain sight in the domestic dog (Canis familiaris)? part 2

@ludwig_muller @ptexis

...continued from https://www.inaturalist.org/posts/56803-an-extinct-canid-canis-rubronegrus-hiding-in-plain-sight-in-the-domestic-dog-canis-familiaris-part-1#

I have just read Smith et al. (2017, https://www.publish.csiro.au/zo/zo17040), which contains important data and analyses.

Please note that the terms 'braininess' and 'EQ', as I use them in this Post, are not synonymous.

This is mainly because EQ (encephalisation quotient)

  • was designed as a species-specific index of braininess relative to the allometric expectations from body mass, and
  • is poorly applicable to the domestic dog (Canis familiaris), with its extreme range of breeds.

EQ in canids tends to complicate rather than to clarify the picture of relative braininess. This is because the domestic dog varies so much in body mass (according to breed) that the ancestral body mass is obscure.

Despite the above complications, Smith et al. (2017) found that

  • the wolf (Canis lupus) is indeed brainier than the domestic dog, with no overlap,
  • the coyote (Canis latrans) and the Eurasian jackal (Canis aureus) seem brainier than the wolf, notwithstanding the fact that the former two spp. are about three-fold smaller-bodied (about 10 kg) than the latter (30 kg), and
  • the black-backed jackal (Lupulella mesomelas) and particularly the side-striped jackal (Lupulella adusta) - despite being 'jackals' - are less brainy than like-size, wild spp. of Canis.

I have reshuffled the data in Smith et al. (2017) as follows, to list all those spp./breeds with body mass about 10 kg, in decreasing order of EQ:

  • Boston terrier 8 kg EQ 164
  • pug 8 kg EQ 158
  • coyote (Canis latrans) 10.5 kg EQ 153
  • miniature schnauzer 7 kg EQ 152.5
  • dachshund 8 kg EQ 145
  • miniature poodle 8 kg EQ 145
  • fox terrier 8 kg EQ 144
  • Eurasian jackal (Canis aureus) 9 kg EQ 142
  • dingo 13 kg, EQ 137
  • wirehaired fox terrier 9 kg EQ 135
  • standard schnauzer 8 kg EQ 135
  • New Guinea singing dog (Canis hallstromi) 11 kg EQ 124.5
  • black-backed jackal (Lupulella mesomelas) 8 kg EQ 121.5
  • short-eared dog (Atelocynus microtis, wild canid of South America) 9 kg EQ 119
  • beagle 14.5 kg EQ 117.5
  • cocker spaniel 13 kg EQ 116
  • bush dog (Speothos venaticus, wild canid of South America) 6 kg EQ 102
  • side-striped jackal (Lupulella adusta) 11 kg EQ 86

How do we interpret the fact that EQ in various breeds of the domestic dog exceeds that in various like-size wild canids? Part of the answer is that EQ was originally conceived as a species-specific quotient.

When applied to breeds within a species, EQ becomes subject to interpretation because of the uncertainty of 'typical' body mass, as follows: EQ exaggerates braininess in small-bodied breeds, and understates braininess in large-bodied breeds.

I assume that the EQ corresponding with the 'real' species-specific EQ of the domestic dog is about 1.0, corresponding to body mass about 20 kg.

Please bear in mind that the point of Smith et al (2017) was the braininess of the dingo relative to the domestic dog; all wild canid spp. were ancillary to their study.

On the above basis, the following picture emerges from Smith et al. (2017).

The domestic dog (excluding the dingo) is less brainy than both the wolf and the Eurasian jackal (C. aureus). It is true that the difference is greater relative to the wolf than relative to the Eurasian jackal. However, relating this to the question of the real main wild ancestor of the domestic dog is rather subjective.

It seems likely that 'Canis rubronegrus' would likewise have been brainier than the domestic dog, based on the finding that all three extant wild spp. of Canis (wolf, coyote, and Eurasian jackal) are brainier than the domestic dog.

So, the data analysed by Smith et al. (2017) do not necessarily undermine the possibility that the domestic dog, with its anthropogenic decephalisation, was mainly derived from an extinct jackal-like (relatively omnivorous, non-gregarious) species rather than the specialised carnivore that is the wolf.

However, the data do suggest that my hypothetical ancestral species, 'Canis rubronegrus', was larger-bodied (about 20 kg) than extant jackals (about 10 kg).

The kelpie breed, with its wild-type conformation and colouration, has body mass 11-20 kg (https://www.perplexity.ai/search/What-is-the-ToObfrkBRw2sKkYuQVAdLg).

The wild ancestor must have been somewhat large-bodied, on average, than the kelpie, if we are to make sense of the EQ values of jackal-size (about 10 kg) breeds of the domestic dog.

In other words, I suggest that 'Canis rubronegrus' was jackal-like in diet and sociality, more than in body size. This would be consistent with Bergmann's rule (https://en.wikipedia.org/wiki/Bergmann%27s_rule), if the ancestral species lived at the northern limit of the vegetated landscape in the Ice Age.

Posted on 24 May, 2024 17:17 by milewski milewski | 2 comments | Leave a comment

The ostrich (Struthio camelus) as a quasi-ungulate, part 6

The only ungulates rivalling the ostrich in length of leg and neck, and diminution of the head, are giraffes (Giraffa) and certain spp. of gazelles. However, all of these use this configuration to reach high rather than to walk far.

The ostrich resembles like-size ungulates in the size of the gastrointestinal tract and other organs, and presumably also digestive power and total metabolic costs.

Among ungulates, body size is associated with ecological separation among spp. of roughly similar shapes.

This is partly because

  • large-bodied forms forage less selectively, and eat poorer foods, than is true for small-bodied forms, while potentially digesting their food more thoroughly, and
  • there are associated differences in height of foraging (Owen-Smith 1985).

Large ungulates with long legs and necks, and small heads with fine muzzles, can potentially coexist with a wide variety of spp., by being more selective (and thus requiring lesser gastrointestinal volumes) than like-size forms, and foraging higher than small-bodied forms.

The ostrich, like e.g. giraffes, seems to maximise selectivity without compromising its mobility. It is potentially able to forage delicately over a wide vertical and horizontal range, thus rivalling ungulates a fraction of its size in the quality of food economically selected.

However, height effectively provides little separation between the ostrich and ungulates, particularly in the sparsest vegetation, where the few shrubs are apparently browsed by gazelles rather than the ostrich. This suggests that horizontal mobility is critical for a bird forced to compete with ungulates for the forbs on which it depends.

In well-vegetated areas, this presumably allows the ostrich to be extremely selective. In barren areas, it may allow the bird to find a sufficient quantity of any food available.

In addition, the ostrich potentially enjoys the flexibility of variable passage rate, since theoretically then food passage in monogastric spp. is independent of fermentation rate (in turn partly a function of food quality). At the same time, it may be able to digest its food more thoroughly than can a gazelle, which it matches in degree of comminution of food and exceeds in fermentation volume, retention time, and gastrointestinal surface area (while requiring scarcely more bulk of food).

If giraffes can be described as tree-specialists of open vegetation, then perhaps the ostrich will be found to be a forb-specialist of open vegetation.

The ostrich, like certain ruminants, is able to survive on a limited quantity of good quality.

The ostrich may use retarded rate of passage of finely-ground food to achieve particularly thorough digestion of limited quantities of food where necessary, rather than processing large quantities of food very superficially as equids potentially do.

This would suit the ostrich to extremely arid areas where the very sparse available vegetation is generally nutrient-rich.

The monogastric competitors of the ostrich are apparently limited by their dependence on

  • drinking water,
  • local, reliable concentrates (suids), and
  • large quantities of food (equids).

Ruminant competitors are limited in ways that favour the ostrich particularly in arid climates. These limitations are in

  • body size,
  • mobility, and
  • digestive power.

The ostrich and equids both coexist with ruminants, but forage with different ratios of quantity to quality. The ostrichnhas the grinding power of ruminants, the fermenting power of equids, and a particularly large area for absorption in the hindgut.

While the ruminant digestive system is specialised for a certain regime of intake rate and fermentation rate, the monogastric/hindgut fermentation system is relatively flexible to variation in quality and quantity of food. Caecal and colonic fermentation capitalise on microbial breakdown of cellulose without the costs of blocking the system (e.g. via an omasal filter) to variable throughput rate. Where grinding is performed by the stomach, it also avoids the costs to foraging time from which cud-chewers suffer - leaving the beak free to keep selecting.

Posted on 24 May, 2024 01:54 by milewski milewski | 6 comments | Leave a comment

23 May, 2024

The ostrich (Struthio camelus) as a quasi-ungulate, part 5

Trophic limitations potentially imposed on any homeothermic herbivorous species (non-coprophagous) of a given body size, and the alternative adaptive strategies of digestion available to the animal.

poor quality of food


  • increased intake, with the effect of substitution of quantity for quality
  • prolonged retention and fermentation of fine fraction (while passing the coarse fraction), which requires sacculation in diverticula rather than the main canal, and has the effect of compensating for limitations on gut-fill, or reliance on body-mobility
  • prolonged retention and fermentation of all food, including coarse fraction, with the effect of microbial production of energy and protein from cellulose

poor quantity of food


  • fine comminution of food, with the effect of boosting the surface area for microbial and enzymatic digestion
  • prolonged retention and fermentation, with the effect of extending the duration of microbial and enzymatic digestion

wide variation in quality of food


  • enlargement of hindgut rather than foregut, with the effect of avoiding wastage by fermentation of available digestible protein
  • sacculation in diverticula, rather than main canal of gastrointestinal tract, with the effect of promoting the speed of passage of food when the rate of fermentation falls below a critical threshold (i.e. in response to a decrease in quality of food)

poverty of energy, rather than protein, in food


  • enlargement of hindgut rather than foregut, with the effect of provision for final assimilation in the small intestine

lack of moisture in food


  • fine comminution, with the effect of retrieval of water from faeces before defecation
  • enlargement of hindgut rather than foregut, with the effect of retrieval of water from faeces before defecation
Posted on 23 May, 2024 23:57 by milewski milewski | 0 comments | Leave a comment