Monday, January 3, 2011

The Chiffchaff and the Aloe

South African aloes were introduced in Gibraltar in the 19th Century. They did well in the Mediterranean climate, similar to that in their home, and spread. They fared best on warm limestone slopes.
The mild, frost-free, winter climate of Gibraltar has allowed the aloes to flower in December and January, the corresponding South African summer.
the slopes take on a spectacular colour as the stands of aloe come into full bloom

These aloes are pollinated in their native South Africa by sunbirds, which have coevolved with the plants and have developed specialised bills for extracting the nectar. The red of the aloes attracts the birds and pollen is transferred by the birds who get their nectar reward. There are no sunbirds in Gibraltar but some species have learnt, in the short time since the 19th Century, that the red aloes mean food.

The main species visiting the aloes is the Chiffchaff, a winter visitor. It seems that the nectar is used as supplement to their usual diet of insects.
Chiffchaffs (above and below) drinking nectar

The Sardinian Warbler, a local resident, is another regular visitor to the aloe stands (above and below)

Sardinian Warblers (male above and female below) are larger than Chiffchaffs and will supplant them from the flowers

but the Chiffchaffs have a trick - they hover and collect nectar from the flower heads that are inaccessible to the heavier Sardinians
So the sunny slopes of Gibraltar in late December and January are a little laboratory with a natural experiment in action. Here we observe a behavioural change in the behaviour of bird populations, both migratory and resident. And, while for a long time the aloes seemed unable to cross pollinate and only spread vegetatively, there is clear evidence now that plants are getting fertilised. The Chiffchaffs are doing the trick, it seems!

Butterfly on aloe - with the warm weather (temperatures around 20C in the middle of the day) many insects are active around the flowers too, providing additional temptation to the insectivorous warblers


  1. Fantastic photography and a very fascinating subject! I am from Cape Town, SA. The aloe is A. arborescens, a native to the southern and eastern coastal and inland mountainous region of South Africa and north to as far as Malawi. It is the most cultivated Aloe species in the world and hybridizes well with other Aloe species.
    In SA we also find a lot of nectar "stealing" by birds other than sunbirds. Weaver birds are the main culprits. Have you noticed this in this particular stand of Aloes?

  2. Thanks Mariana - yes these are arborescens and yes many birds come to the stands, especially House Sparrows which are weaver birds after all! I nearly put a photo of them on the aloes but didn't want to overdo the pics! Thanks for this. Clive

  3. Hey Clive great photos, what a beautiful location to photograph the birds.

  4. Great set of photos Clive. It reminded me when I had an Aloe in my balcony in the centre of Valencia a few years ago and a Chiff-Chaff came to visit. I would't call this 'nectar stealing', they probably polinise the plants too as these flower spikes are adapted to be pollinated for birds in their native range, with a stout stem for birds to perch on, favourite bird colour and pendant flowers.