The sentences are a bit tricky as in each sentence there are a) a reference to a repeatable action (осенью, каждый год = every autumn, every year) b) a reference to a one-direction movement (where to = на юг) However, the adverb "осенью" is placed at the beginning of the first sentence which makes it less significant in the context and emphasizes the link between the verb and "на юг". Thus, the chosen verb is "лететь". Whereas, in the second sentence, "каждый год" is placed right before the verb which emphasizes the aspect of repeatability. Thus, the chosen verb is "летать".

As for me, the first sentence is totally okey and the second one sounds a bit dodgy. I would say that when someone "каждый год осенью летает на юг" it means they fly and return in autumn, like they spend holidays in the south in autumn.

Hi Giordano! It's a tricky question. To me both sentences sound ok, there is a difference between these verbs, but it is very slight. Here it is: - "лететь" implies flying in one particular direction, "head towards" a certain place. - "летать" is about flying there and back, a turnaround motion (= "летят туда, а потом возвращаются"). The opposite choice is possible only for one of these sentences, and it depends on the different adverbs of time that are used. When you use the verb "летают" with an adverb that denotes a period of time, it means that birds fly and return within this same period of time. But with "autumn" it is not possible logically, because birds fly back in spring. But with "каждый год" it is perfectly ok. So, finally you have three options: - Осенью перелётные птицы летят на юг - Перелётные птицы каждый год летают на юг - Перелётные птицы каждый год летят на юг This is bearing in mind what you want or need to emphasize: a motion in one direction only or a two-way motion. If from your context it is clear that it is a trunaround motion, you will use "летают": "Перелетные птицы каждый год летают на юг на зимовку". If you just mean that they head towards a certain place, you will use "летят" (this verb can also be replaced with "улетают" = leave for): "Осенью перелетные птицы летят на юг, а весной возвращаются домой".

Каждый год is as certain as осенью. Thus the second sentence should be "Перелётные птицы каждый год летят на юг". Of course you may adjust: "Перелётные птицы из года в год (постоянно, годами, всю свою жизнь, или часть жизни) летают на юг".

По утрам я встаю, умываюсь, завтракаю и иду на работу - a sequence of my states. I invite you to "follow" me in time as I'm waking up THEN washing THEN eating and then walking. По утрам я встаю, умываюсь, завтракаю и хожу... - immediately somethign changes!!! It doesn't sound as a 'sequence' anymore. SO it sounds silly because the context points at a 'sequence'. "Хожу" means repetition (unless it is "хожу туда-сюда") "По утрам" now does not mean "for each morning there is a routine I follow: 1, 2, 3" as it was with birds. "По утрам" now specifies this repetition of хожу. Now it is a list of various things you do in mornings. A _disordered_ list. This element of listener "following" you disappears. It was created by the "timeflow within a morning", this timeflow (matching the flow and order of speaking) is what was creating the order. Now the listerner "lives" in the time that has many mornings but no flow. And this is why it sounds silly: clearly the speaker is not in the mode of "rememebring various things he does in monrnings'. He is obviously rememberign some morning! He started with "wake up", why do so if you aren't going to start a sequence? the former parse as each morning (I wake up->wash->eat->) the latter as Each morning I wake up, each morning I wash, each morning I eat and I go each morning.