Great egret – Ardea alba
also known as the common egret, large egret or (in the Old World) great white heron,[2][3][4] is a large, widely distributed egret. Distributed across most of the tropical and warmer temperate regions of the world, in southern Europe it is rather localized. In North America it is more widely distributed, and it is ubiquitous across the Sun Belt of the United States and in the Neotropics. The Old World population is often referred to as the great white egret. It is a rare but regular guest in Sweden and has the last couple of years bread in Storsund, Gotland. This year (2015) 16 egrets was seen together in Storsund.

It sounds like this
Recording by John V. Moore from Xeno canto