Threats to the Birds and their Habitat
Threats come in many forms, some very surprising. Here we have listed the main threats, and we are in the process of filling in the details with more text and pictures. Please check back over the next few weeks.
Avian Botulism – Click on this link for a brochure from the USGS National Wildlife Health Center. Read the Wikipedia article for more information.
West Nile Virus – Along with Avian Flu, it has not been found in Hawaii yet, but every dead bird found in the wetland is sent in for testing
Avian Pox – Often seen in songbirds and marine birds, fortunately, this is rarely found in water birds or shorebirds, so it has not been a problem here. It is generally spread by mosquitoes.
Algae Blooms – Hypoxic or anoxic water conditions (low or no dissolved oxygen) can result from algae blooms, and this kills fish. Dead fish can cause avian botulism, so must be removed as soon as possible.
Fish Kills – large fish die-offs can be the result of an algae bloom, but also from pollutants that run into the lake or wetland.
Predators – Endemic
Black-Crowned Night Herons – (Nycticorax nycticorax) This Hawaii native also feeds on chicks.
Barracuda – a three-foot barracuda can easily swallow a chick. Although they don’t come into the shallow water of the wetland, they do frequent the open water where coots often feed.
Oysters – the most unexpected threat to the birds, check out the pictures of a Hawaii Stilt trapped by an oyster.
Predation from Introduced Species
Rats – The biggest threat to the marsh inhabitants. Although we trap constantly, with every heavy rain, more rats are flushed from the storm drains and land on the wetland islands. The waterways do not stop rats, which are excellent swimmers.
Mongoose – We also trap for mongoose, which eats eggs and chicks.
Cattle Egrets – sometimes flocks of 50 or more will descend on the marsh. They prey on all the bird chicks
Bullfrogs – (Rana catesbeiana) in some preserves on Oahu, they are the #1 predator of Hawaiian Stilt chicks. We are actively trapping introduced bullfrogs at Kaelepulu. These are not the same as the common Cane Toads (Rhinella marina), which have much smaller mouths and are not a problem.
Domestic cats – Pet cats are responsible
Mangrove – In some years, we have removed more than 3,000 pounds of mangrove. It requires monthly maintenance because the seeds float in with the wind.
Pluchia and Grasses – fast-growing and very invasive
Papyrus – This popular houseplant loves the wetland habitat and can easily become established.
Batis – the most common plant currently found on the wetland islands, We try to remove it in certain areas to provide habitat for the still. The gallinules do like for cover, however.
Street Run-off – including motor oil and soap from washing cars.
Fertilizers – common garden fertilizers can be toxic to the birds.
Draining Swimming Pools – although, against the law, it still continues. The chlorine kills the food for the native birds.
Release of Pets
Aquarium and Pond Fish –
Turtles – Read-Eared Slider Turtles are now common in the wetland
Seven storm drains empty into the wetland. Run-off carrying dirt, rocks, and silt flows into the wetland with every rain.
Monofilament Fishing Line and Nets
Tangled fishing lines and nets can trap birds, eventually killing them if they are unable to feed or escape from predators.
You wouldn’t think a bird preserve would be threatened by hunting, but in the Spring of 2005 a Koloa Hybrid duck was found shot. This was confirmed by the Fish and Wildlife lab in Madison, Wisconsin.
Every year we collect well over 250 Spray Paint cans from the wetland. They usually appear after a heavy rain, washing down the storm drains. These cans lodge in the vegetation and rust, and the toxic contents leach into the wetland. There is also a constant barrage of water bottles and soft drink cans, that flush down storm drains and channels.