Orange-tufted sunbird

Issue 8, March 1997

Intermediate Tier

Sunbirds are small, brightly coloured birds that are found in Africa and Asia. They range in length from 9 - 30 cm and have a mass of 5 - 20 g. They look like humming- birds and, like them, feed on nectar from flowers. The birds have a tongue rather like a tube which allows them to suck up the nectar more easily.

Male sunbirds are vividly coloured. In some species, the males' colours are further emphasised because they possess long, colourful tail feathers too. By contrast, the females are duller, their feather colour being combinations of greens, greys and browns. Females lay two or three eggs, incubating them for about two weeks. The young are fed at the nest and take two to three weeks to fledge.

One species of sunbird that occurs in Israel is the orange-tufted sunbird. They build a nest of woven grass, leaves, hair and spider webs which they suspend from trees. In a recent study* of these birds the researchers removed the male from a number of nests to see if the behaviour of the female sunbird changed as she tried to compensate for the loss of her mate, i.e. to see if she brought more food to the nest. The scientists recorded the number of visits to the nest, the time spent at the nest and whether or not the bird removed any faecal sacs from the chicks during a visit. The faecal sac, which contains the droppings of the chick, is produced by the chick and collected by the parent bird immediately after feeding. The researchers also recorded the same measures at a series of nests at which both male and female birds were present and caring for their young.

If danger threatens the birds engage in protective behaviour. For example, they mob birds such as jays which might try to steal very young birds or the eggs.

Figure 1. A male orange-tufted sunbird

Figure 2. Results of the observations at the nests of the orange-tufted sunbirds at which the male had been removed:

(a) mean total number of parental visits to the nest per hour
(b) total number of faecal sacs removed per hour
(c) total time spent at the nest per hour
(d) total time spent mobbing (nest guarding) per hour.

1. Suggest one reason why the birds build a nest that hangs from a tree. (1)
2. The birds use leaves, grasses, hair and spider webs to construct their nest. Why do you think these materials would make a suitable nest? (2)
3. Sunbirds in Israel breed mostly in and around towns and cities. Suggest one advantage and one disadvantage to the birds of breeding near human settlements. (2)
4. Using Figure 2(a), estimate how many total visits per hour were made by male- removed lone females (i.e. a female on her own, her mate having been removed). Why is there a difference between the number of visits to the nest by control pairs and by male-removed lone females? (2)
5. Using Figure 2(b), estimate how many faecal sacs per hour are removed from the nest by the lone female. (1)
6. Why do the parent birds remove faecal sacs from the nest? (2)
7. Why do small birds mob predatory birds such as jays, which take chicks from the nest? (2)

* Markham S., Yom-Toy, Y. and Wright, J. 1996. The effect of male removal on female parental care in the orange-tufted sunbird. Animal Behaviour, 52, 43 7 - 444.

Higher Tier

Sunbirds are small, brightly coloured birds that are found in Africa and Asia. They range in length from 9 - 30 em and have a mass of 5 - 20 g. They look like humming- birds and, like them, feed on nectar from flowers. The birds have a tongue rather Re a tube which allows them to suck up the nectar more easily. However, unlike humming- birds, sunbirds perch whilst feeding.

Male sunbirds are vividly coloured. In some species, the males' colours are further emphasised because they possess long, colourful tail feathers too. By contrast, the females are duller, their feather colour being combinations of greens, greys and browns. Females lay two or three eggs, incubating them for about two weeks. The young are fed at the nest and take two to three weeks to fledge.

One species of sunbird that occurs in Israel is the orange-tufted sunbird. They build a nest of woven grass, leaves, hair and spider webs which they suspend from trees. In a recent study* of these birds the researchers removed the male from a number of nests to see if the behaviour of the female sunbird changed as she tried to compensate for the loss of her mate. As well as observing the behaviour of the female the researchers also measured the mass of the chicks. The scientists recorded the number of visits to the nest, the time spent at the nest and whether or not the bird removed any faecal sacs from the chicks during a visit. The faecal sac, which contains the droppings of the chick, is produced by the chick and collected by the parent immediately after feeding. The researchers also recorded the same measures at a series of nests at which both male and female birds were present and caring for their young.

If danger threatens the birds engage in protective behaviour. For example, they mob birds such as jays which might try to steal very young birds or the eggs.

Figure 1. A male orange-tufted sunbird

Figure 2. Results of the observations at the nests of the orange-tufted sunbirds at which the male had been removed:

(a) mean total number of parental visits to the nest per hour
(b) total number of faecal sacs removed per hour
(c) total time spent at the nest per hour
(d) total time spent mobbing (nest guarding) per hour.

1. Sunbirds in Israel breed mostly in and around towns and cities. Suggest one advantage and one disadvantage to the birds of breeding near human settlements. (2)
2. Using Figure 2(b), estimate how many faecal sacs are removed by the male removed lone females. (1)
3. Why do the parent birds remove faecal sacs from the nest?(2)
4. Using Figure 2(d), estimate how much more time control birds spend mobbing than do male removed lone females. (1)
5. Why do small birds mob predatory birds such as jays, which take the chicks in the nest? (2)
6. Figure 3 shows mean chick body mass over the first 14 days of life. Describe the trends that are evident in the graph.

Figure 3. Mean chick mass (g) and chick age (days) for the experimental groups: open circle - control broods; black circle - male-removed broods.


7. What seems to be the main role for both male and female sunbirds in rearing their young? (2)