READ OUT LOUD. Choose which marked text you prefer to practice with - macrons or accent marks - and read the text out loud until you feel comfortable and confident. Then, try reading the unmarked text at the bottom. It should be easy for you after practicing with the marked texts. :-)
MACRONS. Here is the text with macrons:
Accipitrēs quondam ācerrimē inter sē belligerābant. Hōs columbae in grātiam redūcere cōnātae effēcērunt, ut illī pācem inter sē facerent. Quā firmātā, accipitrēs vim suam in ipsās columbās convertērunt. Haec fābula docet potentiōrum discordiās imbēcilliōribus saepe prōdesse.
ACCENT MARKS. Here is the text with ecclesiastical accents, plus some color-coding for the words of three or more syllables (blue: penultimate stress; red: antepenultimate stress):
Accípitres quondam acérrime inter se belligerábant. Hos colúmbae in grátiam redúcere conátae effecérunt, ut illi pacem inter se fácerent. Qua firmáta, accípitres vim suam in ipsas colúmbas convertérunt. Haec fábula docet potentiórum discórdias imbecillióribus saepe prodésse.
UNMARKED TEXT. Here is the unmarked text - after practicing with the marked text that you prefer, you should not have any trouble with the unmarked text:
Accipitres quondam acerrime inter se belligerabant. Hos columbae in gratiam reducere conatae effecerunt, ut illi pacem inter se facerent. Qua firmata, accipitres vim suam in ipsas columbas converterunt. Haec fabula docet potentiorum discordias imbecillioribus saepe prodesse.
IMAGE. Here is an illustration for the story (image source), showing hawks fighting:
