Stan ha de saber qué pájaro es

Stan ha de saber qué pájaro es
 

Hi,

Stan would know what it was

ha de saber; What kind of grammar is this?

Spanish grammar? ;)

In this context, it's a guess. I think Stan knows about birds, so he must know which one this is. :)


- Tocan a la puerta. Ha de ser Pepe. -> I'm expecting Pepe to come and visit me, so I guess it must be him knocking at the door.
- No sé por qué me siento mal. Han de ser los achaques de la edad. -> I feel so old, I assume that the fact I'm feeling ill must because of that.
- No les preguntes a ellos. No han de saber nada. -> Don't bother asking them. They must not know anything.
- Quiero salir pero hace rato había un oso afuera. Ha de seguir ahí. -> I want to go out, but there was a bear outside a few minutes ago. It must still be there.

Is this another way to say have/has to? Like tener que?

Not in this context. "Tener que" rather implies that something is compulsory or that there is need for something, but here I'm only guessing from the information I have. Yet, there is a similar meaning when using "deber de + infinitive":

- Stan debe de saber qué pájaro es éste.
- ...debe de ser Pepe.
- ...deben de ser los achaques de la edad.
- ...no deben de saber nada.
- ...debe de seguir ahí.

Here, the expression "deber de" works as a guess too, there is no obligation. :)