The advantage of bird breeding in the northern region is that the days are long in summer and the nights are short, and the young birds can be fed and nursed in the longer day, which avoids the competition for nesting sites and food in the southern region during various breeding. Moreover, the number of insects in the northern region is richer than that in the southern region in summer, while there are fewer natural enemies in the northern region, and the predation pressure of natural enemies is relatively low. The winter climate in the northern region is very cold, and it often faces the problem of food shortage. In the south, on the other hand, the breeding season is faced with fierce competition for nest sites and food resources, and the predation pressure of natural enemies is also relatively high, but the climate in winter is mild and the food resources in winter are much richer than those in the north. Migratory birds breed in the north in summer and spend the winter in the south in winter. Both places have advantages.
The north here is relative to the tropical areas in the south. In fact, most swallows stay in temperate regions with monsoon climate, not in the very cold north. )
Swallow is a general term for 74 species of passeriformes. Small size, narrow wing tip, short beak and concave tail, weak feet and few feathers. Feathers are monochromatic, blue or green, with metallic luster; Most kinds of men and women are very similar. Swallows spend a lot of time catching pests in the air. It is one of the most flexible birds, mainly feeding on insects such as mosquitoes and flies, and is a well-known beneficial bird. Nest in tree holes or cracks, or make holes in sand dikes, or stick mud on walls or protrusions of corridors, roofs, eaves, etc. In urban and rural areas.