Olive-backed Sunbirds visiting a patch of Scarlet Spiral Flag

posted in: Feeding-plants, Sunbirds, Videography | 0

I have a patch of flowering Scarlet Spiral Flag (Costus woodsonii) in my garden that attract Olive-backed Sunbirds (Nectarinia jugularis) throughout the day. On 11th July 2018, the patch was monitored using a videocam to study the behaviour of the sunbirds visiting the 9 inflorescences, each bearing a single flower. The sunbirds flew in one at a time at various intervals for the nectar. Once on the patch, they moved from flower to flower.

Male Olive-backed Sunbird visiting Scarlet Spiral Flag flower.

Scarlet Spiral Flag is a single stemmed herb with a red inflorescence of closely packed bracts at the top. It belongs to the ginger family Zingiberaceae. A single flower (sometimes two) emerges from the inflorescence each morning, lasting until late evening – see HERE for flower details.

The videocam was set to record the patch of plants in the morning (9-11.40am, see video above) and in the afternoon (1.30-6.00 pm, see video below).

The visits were analysed for frequency of visits, time spent during each visit, number of flowers visited and sex of the sunbirds (male, eclipse male and female). The term “eclipse male” is here used to mean pre-adult (i.e. non-breeding male) after Cheke & Mann (2008). Birds with traces of black on the throat and/or chest are tentatively included under this category. In a future post, I hope to look into this category closely.

Data on morning monitoring:
1. Length of monitoring = 2 hours 40 minutes
2. No. of visits (1 sunbird each time) = 6
3. No. of flowers covered on each visit = 2-7
4. No. of seconds spent at each flower = 1-50
5. Sexes of sunbirds = male, female and male eclipse (young adult)

Data on afternoon monitoring:
1. Length of monitoring = 4 hours 30 minutes
2. No. of visits (1 sunbird each time) = 3
3. No. flowers covered on each visit = 2-6
4. No. of seconds spent at each flower = 30-240
5. Sexes of sunbirds = male and male eclipse (young adult)

More sunbirds visited in the morning, arriving at an average interval of 48 minutes. At each visit, the sunbirds covered 2-7 flowers, spending 0.5-50 minutes at each flower.

The adult male and female sunbirds knew exactly what to do when landing on a flower. Thus they spent short periods feeding on the nectar. In nearly all instances they accessed nectar not by the conventional method of probing from the top of the flower but by forcing the bill through the flower base. This is termed stealing or robbing nectar as such a method does not help in pollination.

The inexperienced sunbirds, the so-called male eclipse (young adult), spent long periods, with one individual taking up to 4 minutes puzzling out how to get at the nectar. This particular individual visited only 2 flowers before flying off.

YC Wee
Singapore
14th July 2018

Reference:
Cheke, R. A. & C. F. Mann, 2008. Family Nectariniidae (Sunbirds). In: del Hoyo, J., A. Elliott & D. A. Christie (eds.), Handbook of the birds of the world. Vol. 13. Penduline-tits to Shrikes. Lynx Editions, Barcelona. Pp. 196-320.

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