$startMonth = date('m-d', strtotime($data['start_date']));
$endMonth = date('m-d', strtotime($data['end_date']));

$result = $this->ModelName->find('all',
    array(
        'conditions' => array(
            'DATE_FORMAT(HealthCareProfessional.dob, "%m-%d") >=' => $startMonth,
            'DATE_FORMAT(HealthCareProfessional.dob, "%m-%d") <=' => $endMonth
        ),
        'order' => 'DATE_FORMAT(HealthCareProfessional.dob, "%m-%d")'
    )
);