Spring migration flows up the east coast on tiny out stretched wings. Hungry from a journey of 1000 plus miles, migrant song birds collapse into green spaces throughout New England. One interesting phenomenon is the “green island” effect. Green islands are essentially green spaces surrounded by the grey concrete and tarmac landscape of the city. Imagine the bird’s eye view of Boston in which thin rivulets of trees and puddles of parks stand out like green oases in a concrete desert. Green islands essentially funnel birds from the surrounding skies and “fall outs” occur especially when northward heading migrants hit a patch of bad weather. Boston's more well known green islands include the Boston Common, Mt. Auburn Cemetery, Arnold Arboretum and even tiny Post Office Square in the financial district. The foresight of early city planners can be accredited for not only preserving space for us to walk, jog, cook out, play baseball, fish, and take evening constitutionals but also for creating a network of urban huts, safe places to refuel, water, rest away the day only to return to the skies at nightfall for another sixty miles in the long journey north. During the month of May Visit any urban patch of tree and field, especially before sunrise, and you may be surprised by what you find.