Individual study: Provision of PVC tube nest boxes for scarlet macaws Ara macao in Tambopata Nature Reserve, Madre de Dios, Peru
Brightsmith D. (2000) Macaw reproduction and management in Tambopata, Peru II: nest box design and use.
Many large macaws (Ara spp.), have experienced large population declines and are now considered endangered, primarily due to habitat destruction and collection for the pet trade. Logging often targets the biggest trees which may have large tree cavities that macaws require for nesting, and collectors may cut nest trees to obtain young birds. As a result, the number of available nest sites for macaws has been greatly reduced. This is compounded by the fact that suitable natural cavities are often naturally very rare, even in pristine forests. The shortage of nest sites may inhibit the recovery of wild macaw populations, even in within nature reserves.
In 1990-91 researchers at the Tambopata Research Center in Peru were the first to successfully produce nest boxes used by wild macaws, with scarlet macaw Ara macao being the first species to breed. The first boxes were made from sections of Ireartea palm trunks but these rotted within less than two nesting seasons (for a summary please see: www.conservationevidence.com/EditEntry.asp?ID=206). In 1992, new boxes made from tropical cedar Cedrella odorata wood proved more successful and durable but still did not last as long as hoped. Therefore a new nest box was designed using PVC tubing.
In response to wooden nest boxes designed for scarlet macaws Ara macoa rotting so quickly, Eduardo Nycander designed a nest box for use at the Tambopata Research Center (TRC) in southeastern Peru, constructed from PVC tubes.
Nest box design: The nest boxes were made from 30 cm or 35 cm diameter piping with tropical cedar Cedrella odorata tops and bottoms. They were lined internally with 5 x 5 cm wire mesh to allow the birds to climb up and down the other wise smooth-surfaced tube. Sand and/or saw dust was placed in the bottom of each tube to provide the birds with a soft substrate upon which to lay their eggs. Each nest had a sliding door to allow researchers to temporarily remove chicks to enable measurements and monitoring of the young to be undertaken.
From August – September 1992, 10 boxes (five 30 cm and five 35 cm diameter) were hung in the forest trees near TRC.
Nest box use and wear: The 30 cm diameter boxes were not used due to a faulty roof design which led to leakage. Of the five 35 cm diameter boxes, scarlet macaws used four in the 1992-1993 nesting season. Since 1993, additional boxes have been constructed and erected. The wooden tops and bottoms rotted away and have now been replaced with metal disks and initial leakage problems have been corrected. In the 1999-2000 season, 12 boxes were available for scarlet macaws, nine of which were used for nesting. Based upon findings from these trials the following design is now used:
PVC tube - 35 cm diameter, with a wall thickness of 4 mm or greater and length, 1.6 m or greater. This is a tough pipe rated for pressurized water. White or light grey pipes are used as it is thought probably the best as these colours absorb less heat than darker colours.
Wire mesh - the entire inside of the tube is lined with 10 or 12 gauge 5 x 5 cm galvanized wire mesh. Care is taken to leave no sharp ends where the wire is cut.
Top and bottom - 2 mm thick aluminum discs are used to cover the top and bottom of the pipes. The top is insulated against the heat by 2-3 cm thick piece of wood attached under the aluminum. Caulk can be used to fill in the holes around the wires on the top or alternatively, flat pieces of PVC can be cut to cover the top and bottom, joined with PVC glue. Wood, rather than aluminum, can be used, but this was found to rot fairly quickly and needed to be regularly replaced. The bottom of boxes are now secured with high quality non-rusting wire as the bottom fell out of one box due to the wires rusting, which resulted in the death a chick.
Door - a square opening about 22 x 22 cm (25 or 30 on large pipes) about 17 – 30 cm up from the bottom is cut and hinged to create a door to access the chicks. Older boxes at TRC used a piece of PVC that is about 20 x 20 cm, mounted so that it can slide up and down over a 15 x 15 cm opening. These doors however, proved a little too small, making it hard to remove older chicks and hinged doors are recommended.
Entrance holes - two entrance holes 17 cm high by 15 cm wide are cut at right angles. The first is about 10 cm from the top of the box and the second is about 20 cm from the top of the box.
Drainage - in the sides of the PVC pipe 6-8 holes (about 4-5 mm in diameter) are drilled 1.5 cm up from the bottom to allow drainage. Another set of drainage holes is drilled about 7-8 cm up the side of the box. Drainage holes can also be drilled in the base itself.
Ventilation holes - Many of the boxes at TRC have ventilation holes (about 10 – 15) drilled throughout the box above the substrate line. This is designed to allow airflow through the box.
Substrate - a layer of gravel is laid in the bottom (to keep the bottom set of drainage holes from clogging up), then a mix of sand and sawdust is overlayed. Sand is effective as it doesn't rot, so even if the sawdust has rotted, there is a soft substrate for the eggs to lie on. It is recommend to fill the bottom of the box up to the bottom of the door, thus chicks are easier to take out and a thick layer is provided (17-30 cm) for the birds to rest on. The boxes weigh from 30-40 kg empty. The total weight depends on the tube thickness and substrate used.
Hanging the boxes - four holes are drilled in the sides of the box near the top and attached by two heavy-duty synthetic rope loops, slotted through the top of the box. These loops are used to tie the box to the tree. Two different independent attachments are recommended so if one breaks the other holds the box in place. Correctly positioned, they will keep the box from spinning in the wind, and when macaws arrive and depart.
Box locations - for scarlet macaws, boxes are hung on the tallest emergent trees available, located in exposed branches or on tree trunks, below or at the level of the lowest foliage. It is also thought good to have the tree isolated as much as possible from other canopy trees which should reduce monkey visitation and associated nest predation.
Conclusions: The PVC tube nest box design is durable and proved successful in attracting breeding scarlet macaws. Attempts are ongoing to attract two other species of macaw in the reserve, blue-and-gold macaw A.ararauna and green-winged macaw A.chloroptera, using nest boxes refined in design specifically for their needs.
Note: If using or referring to this published study, please read and quote the original paper, this can be viewed at: www.duke.edu