What is Ying Ge Yanwu's metaphor?

Ying Ge and Yanwu compared the booming construction scene.

The oriole is singing and the swallow is flying. Describe the noisy and active scene of birds in spring. Combined type; As predicate and attribute; With praise. From the stone "Jinbeiting": "The smoke is red and green, the wind is fragrant, and the Yan dance is long in spring."

Ying Ge Yanwu described spring. Spring, also known as spring, is the first of the four seasons, which refers to the period from beginning of spring to long summer, including solar terms such as beginning of spring, rain, fright, vernal equinox, Qingming and Grain Rain. This is the season when everything comes back to life. Generally, March to May in the Gregorian calendar in the northern hemisphere is designated as spring, and late September to late February in the Gregorian calendar in the southern hemisphere is designated as spring.

In modern meteorology in China, the average temperature in beginning of spring is above 10℃ for five consecutive days. In spring, the climate is warm and mild, and there is rain in most inland areas of China, where everything germinates and the climate is changeable.

Speaking of beginning of spring, people obviously feel that the days are getting longer and the sun is getting warmer. Temperature, sunshine and rainfall are often at the turning point of the year and tend to rise or increase. The growth of crops in early spring is accelerated, and the water consumption for bolting rape and jointing wheat is increased. Irrigation and topdressing should be done in time to promote growth. Agricultural proverbs remind people that "it rains in early spring, get up early and go to bed late", and Da Chun has also begun to prepare for agriculture.