Wednesday, January 7, 2009

Nest Farming: Indonesia, Malaysia: 70% Failure, Philippines: 83% Success, Part II

The esculenta, grass-nest or white-bellied swiftlets are found all over the archipelago. The species also nests in houses, even populated houses. While their nests are virtually worthless, esculenta colonies serve as the host for fostering fuciphaga or white nests swiftlets. In Indonesia, for convenience, fuciphaga is called walet while esculenta is seriti. For our purpose, and following Indonesian practice, I will refer to esculenta as swifts and to fuciphaga as swiftlets.

Having learned from by purpose-built farm failures where I had hoped the birds would follow me, I decided to do the reverse, to follow the birds to their colonies. At this time both my purpose-built farms were still empty.

Swift house colonies abound across our archipelago. Having begun locating these house colonies, I was surprised to find them quiet common. In some instances the owners have given up trying to drive the birds away and have abandoned that part of the house to the birds, usually the living room. I have reports of house colonies from Luzon to Mindanao.

Figure 2. Esculenta house colony in Northern Mindanao. The owner installed wooden ledges under the nests to catch bird droppings.

Having heard of egg-fostering technique from Indonesia, I decided to apply it here. Egg-fostering simply means replacing the swift eggs with swiftlet eggs. The adoptive swift parents raise the swiftlet hatchlings and the fostered birds return to the colony to nests.

Figure 3. Esculenta colony in an inhabited house in Southern Mindanao. The owners had already cleaned out the colony but the birds returned. Swiftlets have a very powerful site fidelity instinct.

There are only two important things to keep in mind when conducting egg-fostering. First, the host colony must number at least 100 nests. This means about 300 birds, including non-nesting juveniles. The colony will still survive should the fostering effort fail. Second, both egg sets must be approximately the same age.

Figure 4. Fostered fuciphaga hatchlings above an older esculenta nestling about to fledge.

Figure 5. Esculenta (left) and fuciphaga (right) nestlings, about the same age. Notice the smaller size and darker, metallic plumage on esculenta and the larger and brownish fuciphaga.

Both species reach sexual maturity in 10-11 months. You should begin to find white nests a little less than a year after the fostering was conducted. After the initial clutch of eggs, and depending on the season, the birds should breed every four months. The first nest will still have some organic material like grass or straw but will already contain more saliva than swift nests. These are called transition nests and are best left alone for at least two breeding cycles.

Figure 6. Transition nest with eggs. Note the higher saliva content but still lower than a mature fuciphaga nest.