well, basically, the 'amazon basin' is kind of like the palm of your hand, and venezuela and peru are just some of the 'fingers' that extend out of it. ALL are connected to the basin to some extent.
Now Peruvians are different than Venezuelans, there is quite some distance between them. Venezuela is the northern tip while Peru is the southwest coast.
Some are advertised as 'Surinam Amazon Basins' , presumably captured in the amazon basin bordering Surinam, or the other way around..
Many of these newer Amazon Basins and Peruvian Amazon Basins are being captured and/or exported from areas very close to Peru and Ecuador.
Many look like common Peruvian Redtails. Some seem a bit lighter, cleaner and contain less melanin, atleast as juveniles.
So, these can be Ecuadorian redtails or normal Peruvian redtails, or a mix of these or more!
The name carries a marketing advantage, as basin animals are sometimes more colorful and less available.
In my opinion, even if you are 1000% gauranteed your 'pair' are 'basins', you could still never be sure on an exact locale! One could contain more peruvian blood, another could contain more brazilian blood. The basin is a melting pot.
It is up to you to choose for looks, or probably take a pair from the same shipment to try to be as consistant as possible.
That's my $.02 in a nutshell... hope this helped.
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Thanks and take care - Joe Rollo
'Tis not the stongest of the species that will eventually survive, nor the most intelligent, but the one most responsive to change' Charles Darwin