Water depth selection, daily feeding routines and diets of waterbirds in coastal lagoons in Ghana

Abstract

Water depth requirements, diet, feeding styles and diurnal activity patterns are described for waterbirds using two brackish water lagoon systems in coastal Ghana, the Songor and Keta Lagoons. We project the habitat and activity data on a guild structure defined on the basis of individual feeding style and the sensory mechanism used to detect food. A total of 3199 flocks containing 118,648 individuals of 36 different waterbird species were examined during October‐November 1994. Feeding habitats varied from dry mudflats to wet mud and shallow water of not more than 20 cm. The depth of water selected by waterbirds for foraging (but not for roosting) was correlated with tarsus length. Foraging birds exhibited a wide range of feeding styles using visual and/or tactile means for detecting prey: pecking, probing, stabbing, sweeping and ploughing, sometimes feeding singly, communally or socially in loose or dense flocks. Prey items taken ranged from seeds of Widgeongrass Ruppia maritima to invertebrates (mainly polychaetes, molluscs and crabs) and fish, mainly juvenile Tilapia. The daytime was spent on two main activities, feeding and roosting, with a small fraction of the time (average of 10% for 25 species) spent on comfort activities. The waterbirds exhibited either a circadian (most waders, except Common Sandpipers Actitis hypoleucos and Turnstones Arenaria interpres) or a diurnal foraging activity pattern (herons and terns), with no purely nocturnal species. Some species fed throughout the day, others showed peak foraging at various times of the day. The proportion of time spent foraging was related to guild (highest in visual and tactile surfaceforaging waders) and was negatively correlated with the size of the species. We conclude that the observed patterns in the use of the 24‐h day by waterbirds for foraging are not species specific but vary depending on conditions on the feeding grounds. Nocturnal foraging is a normal and a regular strategy used by waterbirds to obtain enough food to fulfill their energetic requirements, so that irrespective of the sensory mechanism used to detect prey and the conditions prevailing on the feeding grounds, waterbirds forage day and night as dictated by their energetic needs. Water depth appears to be the key environmental factor controlling the availability of food for the waterbirds in the Ghanaian lagoons.

Distribution and Forage Potential of Some Insect Taxa Sampled with Sweep Nets in the Flood Plains of a Coastal Ramsar Site in Ghana

“…These observations also indicated that the entire flood plain of the lagoon is of a similar patch quality in terms of insect abundance and diversity. Thus the limited ranges and site preferences exhibited by foraging waterbird species in Ghana's coastal lagoons [9] are not governed by disparities in the distribution of the insects.…”

“…According to [8] and [9], different species of waterbirds preferred different foraging microhabitats and utilised limited foraging patches. For instance, while some species of waterbirds preferred and were limited to shoreline habitats, others utilised only marginal water areas or dry vegetation areas [8] [9].…”

“…According to [8] and [9], different species of waterbirds preferred different foraging microhabitats and utilised limited foraging patches. For instance, while some species of waterbirds preferred and were limited to shoreline habitats, others utilised only marginal water areas or dry vegetation areas [8] [9]. Many of these waterbirds, such as the Ringed Plover (Charadrius hiaticula), Grey Plover (Pluvialis squatarola), Curlew Sandpipers (Calidris ferruginea), and Wood Sandpiper (Tringa glareola) feed on insects in coastal Ghana [4] [9] [10].…”

Spatial and temporal fluctuations in presence and use of chironomid prey by shorebirds in the Odiel saltpans, south-west Spain

“…The benthos was sampled every 2 months, selecting four points at random from each pond within the depth range accessible to shorebirds (0-20 cm, Ntiamoa-Baidu et al, 1998). At each point, three core samples were taken to a depth of 3 cm with a 19.6 cm 2 corer.…”

On the Diet and Foraging Strategy of Tundra Waders at Sivash

“…Numerous studies on the foraging of tundra waders during the migration have mainly described and assessed foraging habitats of birds along the East Atlantic Flyway (Recher, 1966;Zwarts et al, 1990;Meltoft e et al, 1994;Le Drean-Quenec'hdu, 1995;Ntiamoa-Baidu et al, 1998). Data on the wader diet at inland bodies of water (Andrusenko, 1980;Shubin, 1999;Shubin, Ivanov, 2005;Sukharev, 2015), including those in the AzovBlack Sea region Verkuil et al, 2003;Khomenko et al, 1999) have been scanty.…”