The timetable of our days

I have been watching the swallows and house martins arrive this spring, but without my usual joy at seeing their return. The numbers of both species have been reducing year on year here. So far this year, I only have one pair of swallows nesting near home; and another pair have just arrived where I work. We used to have dozens in both locations.
I hope that the others will arrive exceptionally late, but I fear they will not appear at all. I am so sad about this. 
I am waiting with trepidation for the arrival of the swifts, which we usually see here sometime in May.
Will they come at all?

Here's the poem that says it for me.

The timetable of our days

Blackbird in the night,

song of thrush at dawn,

buzzard’s blue morning cry,

the lark’s scales rising with the sun,

the calling of crows at dusk,

owls in the first of dark.

Where are the swallows

to twitter on the wires?

The martins, to sweep the eaves

and to shriek their busy schedule?

Where are the proclaimers of summer?

Wait for the scythe of swift,

the scream of their morning,

breathless, so excited to count,

how many this time?

But I wait,

I wait in silence,

the terrible silence, of their absence.

***Donate to the campaign to stop the slaughter of our migrating birds in Malta:
https://www.indiegogo.com/projects/stop-spring-hunting-on-malta#home