Territory of Guam

Guam is an island in the western Pacific Ocean and is an unincorporated insular area of the United States. It is one of five US territories with an established civilian government. The population is less than 175,000 people the majority of whom live in the island’s capital, Hagåtña. Guam is the largest and southernmost of the Mariana Islands.

Guam has an area of 541 km2 (209 square miles), making it the 32nd largest island of the United States, but is the largest island in Micronesia. This island chain was created by the colliding Pacific and Philippine tectonic plates. The Mariana Trench, a deep subduction zone, lies beside the island chain to the east. Challenger Deep, the deepest surveyed point in the Oceans, is southwest of Guam at 10,911 metres deep. The highest point in Guam is Mount Lamlam, which is just 406 metres high. The island is 48 km long and 6 km to 19 km wide. Being at the meeting point of tectonic plates, the island experiences occasional earthquakes. In recent years, earthquakes with epicenters near Guam have had magnitudes ranging from 5.0 to 8.7. Unlike the Anatahan volcano in the Northern Mariana Islands, Guam is not volcanically active. However, due to its proximity to Anatahan, volcanic ash does occasionally affect Guam. The northern part of the island is a forested coralline limestone plateau while the south contains volcanic peaks covered in forest and grassland. A coral reef surrounds most of the island, except in areas where bays exist that provide access to small rivers and streams that run down from the hills into the Pacific Ocean and Philippine Sea.

Inajaran Falls – ©David Burdick/NOAA Public domain via Wikimedia Commons

The climate is characterised as tropical marine. The weather is generally hot and very humid with little seasonal temperature variation. The mean highs of 30 °C and a mean low of 24 °C with an average annual rainfall of 96 inches. The dry season runs from December through June. The remaining months constitute the rainy season. The months of January and February are considered the coolest months of the year with night time temperatures in the mid to low 70’s and generally lower humidity levels. The highest risk of typhoons is during October and November. They can occur, however, year-round.

Birding Guam

Guam has several ecological issues. From the seventeenth through nineteenth centuries, the Spanish introduced pigs, dogs, chickens, the Philippine Deer Cervus mariannus, Black Francolins, and Water Buffalo (known as carabao locally and having cultural significance). Herds of these animals obstruct military base operations and harm native ecosystems. After birth control and adoption efforts were ineffective, the U.S. military began culling the herds (2002).

Mount Lamlam – ©LittleT889 CC BY-SA 4.0 via Wikimedia Commons

Other introduced species include imported Cane Toads, the giant African Snail (an agricultural pest introduced during WWII by Japanese occupation troops) and more recently frog species which could threaten crops in addition to providing additional food for the Brown Tree Snake Boiga irregularis population, which was the most disastrous accidental introduction of all probably by US troops. Reports of loud chirping frogs, known as coquí, that may have arrived from Hawaii have led to fears that the noise could threaten Guam’s tourism. An infestation of the Coconut Rhinoceros Beetle (CRB), Oryctes rhinoceros, has also been detected on Guam (2007). The invasive snake has been responsible for extirpating the majority of the native bird species. Consequently, there are captive breeding programmes with the remaining native birds and attempts to eradicate the snakes. Guam Kingfishers still only exist in captivity, but the Guam Rail is being released from the captive breeding population into two snake-free islands Rota and Cocos. In some areas the snakes have been reduced in numbers by trapping and poisoning with paracetamol laced mice, but up to two million may still remain.