A Party for the Birds

So I’m at the Karongwe Game Reserve this week in the Lowveld region (read ‘savanna wildlife mecca’) of the Limpopo Province. I’m doing a couple of guiding assessments to facilitate the process of young recruits joining the safari industry in SA. I must say, so far the game drives have been excellent (*FGASA/Theta you can be proud of your latest additions). This morning we headed out with the intention to look for birds and birding is what we got! Its winter and the veld is rather dry although not completely leafless yet. The air is chilly and bites the tip of your nose as you drive along but it’s magic all the same. I have to keep my binoculars under my jacket so that they don’t mist up each time I lift them to my eyes. The improved visibility from the wilting bush helps with spotting birds especially in the early morning when most species are vying for the sun in the upper-most branches. This morning, the attempts of a pearl-spotted owlet to warm up attracted more than he (or we bargained for). In the tree, about 15 different bird species had gathered to independently chirp their disapproval at the small predator. Of the bullies there was green-winged pytilia, yellow-fronted tinkerbird, Stierlings wren-warbler, yellow-breasted apalis, long-billed crombec, blue waxbills (galore), chin-spot batis, a woodpecker species or two, black-headed oriole, southern black tits and fork-tailed drongo.

This behaviour is known as mobbing and is a tactic used to encourage the raptor to leave the vicinity. The small birds recognize the owlet as a predatory threat (even though peal-spotted owlets eat mainly insects) but are letting the raptor know that it has been spotted and no longer holds any kind of element of surprise to attack the ‘potential prey’.

Birds of different species frequently associate in mixed feeding parties and are found together in what is known as a ‘bird party’. Generally the species in a bird party are predominantly insect eaters and each level or strata of birds feeding in the vegetation, benefits from the activity of the ones above it, dropping or herding insects to one another. A common food resource generally attracts the birds to form mixed parties and in the case of fruiting or flowering trees, not only will the frugivorous and nectarivorous birds be drawn to the location but so too will insects. In turn the insect eating birds arrive (and possibly also predatory ones). While the birds in the higher levels of vegetation move and feed they may knock seeds down to the smaller seed-eaters below. The collective feasting effort of a bird party affords all the birds in the area shared vigilance and they are better able to look out for danger and provide early warning of it (and then take action against it as in the case of the pearl-spotted owlet).

Bird parties are a type of interspecific (between species) allelomimetic behaviour. Allelomimetic behaviour relates to ‘copy-cat’ behaviour practiced predominantly by gregarious bird species. For example blue waxbills form monogamous pairs but during the day they feed together in flocks for greater protection keeping constant contact with each other through high-pitched ‘tswees’. If one bird suddenly flies off, the entire flock will also fly away. As far as bird parties are concerned, one or two birds begin feeding earnestly and other species notice this and join in ‘mimicking’ the original birds behaviour until a large party forms.

*FGASA: stands for the “Field guides association of southern Africa” and is the standards and training regulator for the guiding industry in southern Africa.
Theta: stands for “Tourism, hospitality and sports education training authority” and represents the South African government’s “National Qualifications Framework” in these fields. This framework facilitates the upskilling of people in industry and ensures an appropriate level of competence in the workplace. Once a FGASA / Theta skills program has been achieved, a candidate registers to operate as a guide legally in RSA with DEAT (Dept of Environmental Affairs and Tourism) (see http://www.fgasa.co.za/ for more info)

Toad-ally Cool

So I was scrolling through the latest edition of "Under Currents" which is Cape Town's Two Ocean's Aquarium publication and a remarkable story caught my eye about an endangered Western leopard toad that had been rescued from literally under the wheel of a car and rehabilitated for the sake of 'saving the species'. In all my years out in the bundu's, I'd never heard of a frog being given veterinary treatment before - anesthetic and antibiotic injections included! Furthermore, his tongue had been irreparably damaged and was amputated as a result implying he could no longer swallow. Frogs use their tongues to push their food towards the back of the mouth and then jam it down the throat using their eyeballs. In spite of this set-back for 'Teddy' (as he has been dubbed...to my dismay as I'm not really pro the anthropomorphism of wildlife but it does help with fostering public support) and a period of undignified force-feeding, the one-eyed toad made a miraculous recuperation and began lunging and swallowing of his own accord. Unfortunately he won't ever rejoin a wild population but is now housed at the aquarium in a very prestigious ambassadorial position!

So whats the big deal about a toad getting a second chance? The fact of the matter is that frogs are indicators of the state of the environment. Because they have such moist, porous skins, they tend to absorb toxins much more easily that other scaled or furred creatures and are usually the first to disappear from an environment because of poisoning. Scientists typically guage the health of a habitat by the occurence of frog species. Toads are one group of frogs...one that yes, has more warty skin than most but this is simply an adapatation to the type of habitat they live in. The bumps on the skin create an uneven surface that acts as camoflage as they move around on the ground. Of the 'frogs', toads are the most terrestrial. Touching a toad will not give a person warts although they do have enlarged parotid glands on the head which secrete toxins as a defence when they are picked up by something (the toxin is what causes dogs mouths to froth when they grab toads).

The Western Leopard Toad occurs as a very small population in two isolated locatilities in the Cape and not much is really known about its survival success at the moment because they're so rare. Every member is considered vital for the perpetuation of the species. Of the frog species found in South Africa, more than half are found in the Western Cape (a whopping 62 spp) of which 29 species are found no where else in the world! Due to the fact that cities and farm lands expand so rapidly in our day and age, the habitats needed by all creatures but primarily the sensitive frogs are being diminished. This in conjunction with a rogue chytrid fungus that affects all frogs is wiping them out to the point that we're headed to the single largest mass extinction since the dinosaurs!

Sad state of affairs but I guess my take on the matter is that we should all try to appreciate what we've got while we have it (hop on down to Two Oceans and visit their new frog exhibit http://www.aquarium.co.za/ or see frogs on display at uShaka Marine World in Durban or Cango Wildlife Ranch in Oudtshoorn). Painted reed frogs (blogged about yesterday and the day before) and grey tree frogs often hide-out in human habitations to see through the winter (dry season)...who doesn't want to hiberate...have a look at them but don't chase them away or freak-out (they eat insects not humans). There are some practical things that 'Under Currents' suggests that one can do to encourage frogs in your garden like having a few upturned flower-pots under which they can hide, a net affixed to the side of the swimming pool to allow them to climb out after their dip (otherwise they usually drown coz there's no way out), beware of toxins you're using in the garden, create escape passages under / through the garden wall (only need be big enough for the frog not a burglar!) and try not to drive over the little critters during the rainy season.

The Chinese see a toad in the moon - not a man - and a lunar eclipse is the result of said amphibian trying to swallow the 'big cheese' itself...a bit extreme maybe but I hope a reminder to all of us of how toad-ally cool and (necessary in the bigger picture) frogs are!

(pic from http://www.flickr.com/)

Frog Voices

Frogs are a favorite nature subject for me (and the reason I have one tatooed onto my hip!). Its the middle of winter here in South Africa and a strange time to be writing about them but perhaps its because I miss the insane caucophony they produce after the rains and throughout a good wet summer. Its one of the charms of wild Africa and as you travel through the bush moving past different habitats the volume and pitch of these small creatures varies from deafening to charming. Its no wonder that a chorus of frogs is known as an antiphony - it certainly is the opposite of a symphony. The reason for this is that there are a number of purposes for which frogs call and a number of different calls that they make:

The most common, incessant calls heard at night are the advertisements of the males singing to attract females. These calls are unique to individual species and attract members of similar species to a particular area and then help the males to space themselves out relative to one another. Although the resultant sound is somewhat frenzied (and confusing to predators wishing to isolate a single frog as a meal), the group chorus does have a degree of order. Two nearby callers will in fact alternate their sounds so that they don’t interfere with one another. This is called timeshare calling and it makes it easier for females to isolate their choice of mate which will depend on his pitch, a deeper tone usually representing a bigger and genetically superior male.

Should one male intrude on another individual’s turf, he may utter aggressive calls to denote his hold over that territory. These are usually heard early on in an evening while the frogs are still establishing their calling sites for the evening. Prime calling sites are in demand since females will select mates based on their calling sites since genetically superior individuals are likely to secure the best sites. To this end, males will even fight, wrestling and kicking to displace one another (as is the case with the painted reed frogs shown in the image and profiled below). Some males maximize on the efforts of the individuals in better calling sites (or with stronger calls) by remaining silent and then intercepting females attracted to these males in prime positions. This is called satellite behaviour.

Females produce a specific call called a release call to indicate to the male that they have completed laying and that he can let go. Sometimes when males are mistakenly grabbed by other males, they too will utter release calls. Distress calls are given by both sexes should they be seized by predators. This is often adequate to startle the predator which then releases the frog.

Frogs are fabulous

As their name suggests, reed frogs make use of the tall reed beds that fringe pans to breed. The males climb right to the top of the reeds to emanate their shrill calls. Reed frogs have flat toe pads to assist in climbing the reeds. Each call site is defended from other males and reed frogs are notorious for screeching and kicking to displace a rival. During the day reed frogs may hide in trees taking shelter in the axils of leaves. If no tree cover is available, they will simply remain on the reed stalk sometimes in exposed positions. Their small bodies and hunched posture allows them to minimize evaporative losses at these times.

This is a small frog of only about 2.5cm but is conspicuous for its dazzling colouration and high pitched piping whistle that creates a notable cacophony when many call in chorus. Painted reed frogs are common and occurs throughout the eastern part of southern Africa in a variety of different races (up to 16) each possessing unique colours and patterns which have caused great consternation amongst scientists with regards to classification. The colour form present in the Lowveld is strikingly striped in black, white and yellow on the upper side and the flanks and limbs are fringed with red patches. To create further confusion, painted reed frogs are able to bleach their colouration completely during the day in order to thermoregulate (reflect heat).

The inner sections of the hind legs are infused red and this is used as an anti-predatory device known as flash colouration. A threatened individual will leap up, exposing the bright red colour obvious to the predator which then focuses on this. As the frog lands, the red inner leg is instantly tucked away and the predator no longer has its target in sight and may then struggle to relocate its quarry should the frog remain motionless.