Here are some of the challenges he encounters:
* The curse of the Adarna bird: Don Pedro is the first to be sent to capture the magical bird. He is cursed by the bird's song, which lulls him into a deep sleep and causes him to become bedridden. He is unable to fulfill his father's wishes and ultimately, his fate is left uncertain.
* The challenge of the seven mountains: The Adarna bird resides in a mystical forest, guarded by seven mountains, each with its own unique challenge. Don Pedro has to navigate through these mountains, enduring difficult conditions and facing dangerous creatures. He is unable to overcome these obstacles and fails to capture the Adarna.
* His lack of perseverance and determination: Unlike his brothers, Don Pedro doesn't possess the same level of determination and perseverance. He succumbs to the Adarna's curse and doesn't push through the challenges.
* He is overshadowed by his brothers: Don Diego and Don Juan, his brothers, are more successful in their quest for the Adarna. They display greater resilience and ultimately achieve what Don Pedro could not.
Overall, Don Pedro's difficulties stem from a combination of external factors, such as the magical curse, and internal flaws like his lack of willpower and tenacity. This ultimately leads to his failure and sets the stage for his brothers to take on the challenge.